The Project Gutenberg EBook of Elements of Structural and Systematic Botany, by Douglas Houghton Campbell This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.org Title: Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Author: Douglas Houghton Campbell Release Date: January 17, 2007 [EBook #20390] Language: English Character set encoding: ISO-8859-1 *** START OF THIS PROJECT GUTENBERG EBOOK SYSTEMATIC BOTANY *** Produced by Marilynda Fraser-Cunliffe, Laura Wisewell and the Online Distributed Proofreading Team at http://www.pgdp.net E L E M E N T S OF STRUCTURAL AND SYSTEMATIC BOTANY, FOR HIGH SCHOOLS AND ELEMENTARY COLLEGE COURSES. BY DOUGLAS HOUGHTON CAMPBELL, PH.D., PROFESSOR OF BOTANY IN THE INDIANA UNIVERSITY. BOSTON, U.S.A.: PUBLISHED BY GINN & COMPANY. 1890. COPYRIGHT, 1890, BY DOUGLAS HOUGHTON CAMPBELL. ALL RIGHTS RESERVED. TYPOGRAPHY BY J. S. CUSHING & CO., BOSTON, U.S.A. PRESSWORK BY GINN & CO., BOSTON, U.S.A. PREFACE. THE RAPID ADVANCES MADE IN THE SCIENCE OF BOTANY WITHIN THE LAST FEW YEARS NECESSITATE CHANGES IN THE TEXT BOOKS IN USE AS WELL AS IN METHODS OF TEACHING. HAVING, IN HIS OWN EXPERIENCE AS A TEACHER, FELT THE NEED OF A BOOK DIFFERENT FROM ANY NOW IN USE, THE AUTHOR HAS PREPARED THE PRESENT VOLUME WITH A HOPE THAT IT MAY SERVE THE PURPOSE FOR WHICH IT IS INTENDED; VIZ., AN INTRODUCTION TO THE STUDY OF BOTANY FOR USE IN HIGH SCHOOLS ESPECIALLY, BUT SUFFICIENTLY COMPREHENSIVE to serve also as a beginning book in most colleges. IT DOES NOT PRETEND TO BE A COMPLETE TREATISE OF THE WHOLE SCIENCE, AND THIS, IT IS HOPED, WILL BE SUFFICIENT APOLOGY FOR THE ABSENCE FROM ITS PAGES OF MANY IMPORTANT SUBJECTS, ESPECIALLY PHYSIOLOGICAL TOPICS. IT WAS FOUND IMPRACTICABLE TO COMPRESS WITHIN THE LIMITS OF A BOOK OF MODERATE SIZE ANYTHING LIKE A THOROUGH DISCUSSION OF EVEN THE MOST IMPORTANT topics of all THE DEPARTMENTS OF BOTANY. AS A THOROUGH UNDERSTANDING OF THE STRUCTURE OF ANY ORGANISM FORMS THE BASIS OF ALL FURTHER INTELLIGENT STUDY OF THE SAME, IT HAS SEEMED TO THE AUTHOR PROPER TO EMPHASIZE THIS FEATURE IN THE PRESENT WORK, which is professedly an introduction, only, to the science. THIS STRUCTURAL WORK HAS BEEN SUPPLEMENTED BY SO MUCH CLASSIFICATION AS WILL SERVE TO MAKE CLEAR THE RELATIONSHIPS OF DIFFERENT GROUPS, AND THE PRINCIPLES UPON WHICH THE CLASSIFICATION IS BASED, AS WELL AS ENABLE THE STUDENT TO RECOGNIZE THE COMMONER TYPES OF THE DIFFERENT GROUPS AS THEY ARE MET WITH. THE AIM OF THIS BOOK IS NOT, HOWEVER, MERELY THE IDENTIFICATION OF PLANTS. WE WISH HERE TO ENTER A STRONG PROTEST AGAINST THE ONLY TOO PREVALENT IDEA THAT THE CHIEF AIM OF BOTANY IS THE ABILITY TO RUN DOWN A PLANT BY MEANS OF AN “ANALYTICAL KEY,” THE SUBJECT BEING EXHAUSTED AS SOON AS THE NAME OF THE PLANT IS DISCOVERED. A KNOWLEDGE OF THE PLANT ITSELF IS FAR MORE IMPORTANT THAN ITS NAME, HOWEVER DESIRABLE IT may be to know the latter. IN SELECTING THE PLANTS EMPLOYED AS EXAMPLES OF THE DIFFERENT GROUPS, SUCH WERE CHOSEN, AS FAR AS POSSIBLE, AS ARE EVERYWHERE COMMON. OF COURSE THIS WAS NOT ALWAYS POSSIBLE, AS SOME IMPORTANT FORMS, e.g. THE RED AND BROWN SEAWEEDS, ARE NECESSARILY NOT ALWAYS READILY PROCURABLE BY ALL STUDENTS, BUT IT WILL BE FOUND THAT THE GREAT MAJORITY OF THE FORMS USED, OR CLOSELY RELATED ONES, ARE WITHIN THE REACH OF NEARLY ALL STUDENTS; AND SUCH DIRECTIONS ARE GIVEN FOR COLLECTING AND PRESERVING THEM AS WILL MAKE IT POSSIBLE EVEN FOR THOSE IN THE LARGER CITIES TO SUPPLY THEMSELVES WITH THE NECESSARY MATERIALS. SUCH DIRECTIONS, TOO, FOR THE MANIPULATION AND EXAMINATION OF SPECIMENS ARE GIVEN AS WILL MAKE THE BOOK, IT IS HOPED, A LABORATORY GUIDE AS WELL AS A MANUAL OF CLASSIFICATION. INDEED, IT IS PRIMARILY INTENDED THAT THE BOOK should so serve as a help in the study of the actual specimens. Although much can be done in the study, even of the lowest plants, without microscopic aid other than a hand lens, FOR A THOROUGH UNDERSTANDING OF THE STRUCTURE OF ANY PLANT A GOOD COMPOUND MICROSCOPE IS INDISPENSABLE, AND WHEREVER IT IS POSSIBLE THE STUDENT SHOULD BE PROVIDED WITH SUCH AN INSTRUMENT, TO USE THIS BOOK TO THE BEST ADVANTAGE. AS, HOWEVER, MANY ARE NOT ABLE TO HAVE THE USE OF A MICROSCOPE, THE GROSS ANATOMY OF ALL THE FORMS DESCRIBED HAS BEEN CAREFULLY TREATED FOR THE ESPECIAL BENEFIT OF SUCH STUDENTS. SUCH PORTIONS OF THE TEXT, AS WELL AS THE GENERAL DISCUSSIONS, ARE PRINTED IN ORDINARY TYPE, WHILE THE MINUTE ANATOMY, AND ALL POINTS REQUIRING MICROSCOPIC AID, ARE DISCUSSED IN separate paragraphs printed in smaller type. THE DRAWINGS, WITH VERY FEW EXCEPTIONS, WHICH ARE DULY CREDITED, WERE DRAWN FROM NATURE BY THE AUTHOR, AND nearly all expressly for this work. A LIST OF THE MOST USEFUL BOOKS OF REFERENCE IS APPENDED, ALL OF WHICH HAVE BEEN MORE OR LESS CONSULTED IN THE preparation of the following pages. THE CLASSIFICATION ADOPTED IS, WITH SLIGHT CHANGES, THAT GIVEN IN GOEBEL’S “OUTLINES OF MORPHOLOGY AND CLASSIFICATION”; WHILE, PERHAPS, NOT IN ALL RESPECTS ENTIRELY SATISFACTORY, IT SEEMS TO REPRESENT MORE NEARLY THAN ANY OTHER OUR PRESENT KNOWLEDGE OF THE SUBJECT. CERTAIN GROUPS, LIKE THE DIATOMS AND Characeæ, ARE PUZZLES TO THE BOTANIST, AND at present it is impossible to give them more than a provisional place in the system. IF THIS VOLUME SERVES TO GIVE THE STUDENT SOME COMPREHENSION OF THE REAL AIMS OF BOTANICAL SCIENCE, AND ITS CLAIMS to be something more than the “Analysis” of flowers, it will have fulfilled its mission. DOUGLAS H. CAMPBELL. BLOOMINGTON, INDIANA, October, 1889. [Page iii] [Page iv] [Page v] [Page vi] TABLE OF CONTENTS. [Page vii] CHAPTER I.—INTRODUCTION Composition of Matter; Biology; Botany; Zoölogy; Departments of Botany; Implements and Reagents; Collecting Specimens. CHAPTER II.—THE CELL Parts of the Cell; Formation of New Cells; Tissues. CHAPTER III.—CLASSIFICATION OF PLANTS Protophytes; Slime-moulds; Schizophytes; Blue-green Slimes, Oscillaria; Schizomycetes, Bacteria; Green Monads, Euglena, Volvox. CHAPTER IV.—ALGÆ Classification of Algæ; Green Algæ; Protococcaceæ, Protococcus; Confervaceæ, Cladophora, Œdogonium, Coleochæte. CHAPTER V.—GREEN ALGÆ (Continued) Pond-scums, Spirogyra; Siphoneæ, Vaucheria; Characeæ, Chara. CHAPTER VI.—BROWN SEAWEEDS Diatomaceæ; True Brown Algæ, Fucus; Classification of Brown Algæ. CHAPTER VII.—RED ALGÆ Structure of Red Algæ; Callithamnion; Fresh-Water Forms. PAGE 1 6 9 21 30 41 49 [Page viii] CHAPTER VIII.—FUNGI Phycomycetes, Mycomycetes; Phycomycetes, Black Moulds, Mucor; White Rusts and Mildews, Cystopus; Water Moulds. CHAPTER IX.—TRUE FUNGI Yeast; Smuts; Ascomycetes; Dandelion Mildew; Cup Fungi, Ascobolus; Lichens; Black Fungi. CHAPTER X.—TRUE FUNGI (Continued) Basidiomycetes; Rusts; Coprinus; Classification. CHAPTER XI.—BRYOPHYTES Classification; Liverworts, Madotheca; Classification of Liverworts; Mosses, Funaria; Classification of Mosses. CHAPTER XII.—PTERIDOPHYTES Bryophytes and Pteridophytes; Germination and Prothallium; Structure of Maiden-hair Fern. CHAPTER XIII.—CLASSIFICATION OF PTERIDOPHYTES Ferns; Horse-tails; Club Mosses. CHAPTER XIV.—SPERMAPHYTES General Characteristics; Gymnosperms and Angiosperms, Scotch-pine; Classification of Gymnosperms. CHAPTER XV.—SPERMAPHYTES (Continued) Angiosperms; Flowers of Angiosperms; Classification of Angiosperms; Monocotyledons, Structure of Erythronium. CHAPTER XVI.—CLASSIFICATION OF MONOCOTYLEDONS Liliifloræ; Enantioblastæ; Spadicifloræ; Glumaceæ; Scitamineæ; Gynandræ, Helobiæ. CHAPTER XVII.—DICOTYLEDONS General Characteristics; Structure of Shepherd’s-purse. 54 63 77 86 102 116 128 143 153 170 [Page ix] CHAPTER XVIII.—CLASSIFICATION OF DICOTYLEDONS Choripetalæ: Iulifloræ; Centrospermæ; Aphanocyclæ; Eucyclæ; Tricoccæ; Calycifloræ. CHAPTER XIX.—CLASSIFICATION OF DICOTYLEDONS (Continued) Sympetalæ: Isocarpæ, Bicornes, Primulinæ, Diospyrinæ; Anisocarpæ, Tubifloræ, Labiatifloræ, Contortæ, Campanulinæ, Aggregatæ. 181 210 BOTANY. CHAPTER I. INTRODUCTION. ALL MATTER IS COMPOSED OF CERTAIN CONSTITUENTS (ABOUT SEVENTY ARE AT PRESENT KNOWN), WHICH, SO FAR AS THE CHEMIST is concerned, are indivisible, and are known as elements. OF THE INNUMERABLE COMBINATIONS OF THESE ELEMENTS, TWO GENERAL CLASSES MAY BE RECOGNIZED, ORGANIC AND INORGANIC BODIES. WHILE IT IS IMPOSSIBLE, OWING TO THE DEPENDENCE OF ALL ORGANIZED MATTER UPON INORGANIC MATTER, TO GIVE AN ABSOLUTE DEFINITION, WE AT ONCE RECOGNIZE THE PECULIARITIES OF ORGANIC OR LIVING BODIES AS DISTINGUISHED FROM INORGANIC OR NON-LIVING ONES. ALL LIVING BODIES FEED, GROW, AND REPRODUCE, THESE ACTS BEING THE RESULT OF THE ACTION OF FORCES RESIDENT WITHIN THE ORGANISM. INORGANIC BODIES, ON THE OTHER HAND, REMAIN, AS A RULE, UNCHANGED SO LONG AS THEY ARE NOT ACTED upon by external forces. ALL LIVING ORGANISMS ARE DEPENDENT FOR EXISTENCE UPON INORGANIC MATTER, AND SOONER OR LATER RETURN THESE ELEMENTS TO THE SOURCES WHENCE THEY CAME. THUS, A PLANT EXTRACTS FROM THE EARTH AND AIR CERTAIN INORGANIC COMPOUNDS WHICH ARE CONVERTED BY THE ACTIVITY OF THE PLANT INTO A PART OF ITS OWN SUBSTANCE, BECOMING THUS INCORPORATED INTO A LIVING ORGANISM. AFTER THE PLANT DIES, HOWEVER, IT UNDERGOES DECOMPOSITION, AND THE ELEMENTS ARE RETURNED AGAIN TO THE EARTH AND atmosphere from which they were taken. INVESTIGATION HAS SHOWN THAT LIVING BODIES CONTAIN COMPARATIVELY FEW ELEMENTS, BUT THESE ARE COMBINED INTO extraordinarily COMPLEX COMPOUNDS. THE FOLLOWING ELEMENTS APPEAR TO BE ESSENTIAL TO ALL LIVING BODIES: CARBON, HYDROGEN, OXYGEN, NITROGEN, SULPHUR, POTASSIUM. BESIDES THESE THERE ARE SEVERAL OTHERS USUALLY PRESENT, BUT NOT apparently essential to all organisms. These include phosphorus, iron, calcium, sodium, magnesium, chlorine, silicon. AS WE EXAMINE MORE CLOSELY THE STRUCTURE AND FUNCTIONS OF ORGANIC BODIES, AN EXTRAORDINARY UNIFORMITY IS APPARENT IN ALL OF THEM. THIS IS DISGUISED IN THE MORE SPECIALIZED FORMS, BUT IN THE SIMPLER ONES IS VERY APPARENT. OWING TO THIS ANY attempt to separate absolutely the animal and vegetable kingdoms proves futile. THE SCIENCE THAT TREATS OF LIVING THINGS, IRRESPECTIVE OF THE DISTINCTION BETWEEN PLANT AND ANIMAL, IS CALLED “BIOLOGY,” BUT FOR MANY PURPOSES IT IS DESIRABLE TO RECOGNIZE THE DISTINCTIONS, MAKING TWO DEPARTMENTS OF BIOLOGY,—BOTANY, treating of plants; and Zoölogy, of animals. It is with the first of these only that we shall concern ourselves here. WHEN ONE TAKES UP A PLANT HIS ATTENTION IS NATURALLY FIRST DRAWN TO ITS GENERAL APPEARANCE AND STRUCTURE, WHETHER IT IS A COMPLICATED ONE LIKE ONE OF THE FLOWERING PLANTS, OR SOME HUMBLER MEMBER OF THE VEGETABLE KINGDOM,—A MOSS, SEAWEED, TOADSTOOL,—OR EVEN SOME STILL SIMPLER PLANT LIKE A MOULD, OR THE APPARENTLY STRUCTURELESS GREEN SCUM THAT FLOATS ON A STAGNANT POND. IN ANY CASE THE IMPULSE IS TO INVESTIGATE THE FORM AND STRUCTURE AS FAR AS THE MEANS AT ONE’S DISPOSAL WILL PERMIT. SUCH A STUDY OF STRUCTURE CONSTITUTES “MORPHOLOGY,” WHICH INCLUDES TWO DEPARTMENTS,—GROSS ANATOMY, OR A GENERAL STUDY OF THE PARTS; AND MINUTE ANATOMY, OR “HISTOLOGY,” IN WHICH A MICROSCOPIC EXAMINATION IS MADE OF THE STRUCTURE OF THE DIFFERENT PARTS. A SPECIAL DEPARTMENT OF MORPHOLOGY CALLED “EMBRYOLOGY” IS OFTEN RECOGNIZED. THIS EMBRACES A STUDY OF THE DEVELOPMENT OF THE ORGANISM FROM ITS EARLIEST STAGE, AND ALSO THE DEVELOPMENT of its different members. FROM A STUDY OF THE STRUCTURE OF ORGANISMS WE GET A CLUE TO THEIR RELATIONSHIPS, AND UPON THE BASIS OF SUCH RELATIONSHIPS ARE ENABLED TO CLASSIFY THEM OR UNITE THEM INTO GROUPS SO AS TO INDICATE THE DEGREE TO WHICH THEY ARE related. This constitutes the division of Botany usually known as Classification or “Systematic Botany.” FINALLY, WE MAY STUDY THE FUNCTIONS OR WORKINGS OF AN ORGANISM: HOW IT FEEDS, BREATHES, MOVES, REPRODUCES. THIS IS “Physiology,” and like classification must be preceded by a knowledge of the structures concerned. FOR THE STUDY OF THE GROSS ANATOMY OF PLANTS THE FOLLOWING ARTICLES WILL BE FOUND OF GREAT ASSISTANCE: 1. A SHARP KNIFE, AND FOR MORE DELICATE TISSUES, A RAZOR; 2. A PAIR OF SMALL, FINE-POINTED SCISSORS; 3. A PAIR OF MOUNTED NEEDLES (THESE CAN BE MADE BY FORCING ORDINARY SEWING NEEDLES INTO HANDLES OF PINE OR OTHER SOFT WOOD); 4. A HAND LENS; 5. DRAWING- paper and pencil, and a note book. FOR THE STUDY OF THE LOWER PLANTS, AS WELL AS THE HISTOLOGY OF THE HIGHER ONES, A COMPOUND MICROSCOPE IS INDISPENSABLE. INSTRUMENTS WITH LENSES MAGNIFYING FROM ABOUT 20 TO 500 DIAMETERS CAN BE HAD AT A COST VARYING FROM about $20 to $30, and are sufficient for any ordinary investigations. OBJECTS TO BE STUDIED WITH THE COMPOUND MICROSCOPE ARE USUALLY EXAMINED BY TRANSMITTED LIGHT, AND MUST BE TRANSPARENT ENOUGH TO ALLOW THE LIGHT TO PASS THROUGH. THE OBJECTS ARE PLACED UPON SMALL GLASS SLIPS (SLIDES), CHAPTER XX.—FERTILIZATION OF FLOWERS CHAPTER XXI.—HISTOLOGICAL METHODS Nuclear Division in Wild Onion; Methods of Fixing, Staining, and Mounting Permanent Preparations; Reference Books. INDEX 225 230 237 [Page 1] [Page 2] [Page 3] Fig. 1. MANUFACTURED FOR THE PURPOSE, AND COVERED WITH EXTREMELY THIN PLATES OF GLASS, ALSO SPECIALLY MADE. IF THE BODY TO BE EXAMINED IS A LARGE ONE, THIN SLICES OR SECTIONS MUST BE MADE. THIS FOR MOST PURPOSES MAY BE DONE WITH AN ORDINARY RAZOR. MOST PLANT TISSUES ARE BEST EXAMINED ORDINARILY IN WATER, THOUGH OF COURSE SPECIMENS SO MOUNTED CANNOT BE preserved for any length of time. IN ADDITION TO THE IMPLEMENTS USED IN STUDYING THE GROSS ANATOMY, THE FOLLOWING WILL BE FOUND USEFUL IN HISTOLOGICAL WORK: 1. A SMALL CAMEL’S-HAIR BRUSH FOR PICKING UP SMALL SECTIONS AND PUTTING WATER IN THE SLIDES; 2. SMALL FORCEPS FOR HANDLING DELICATE OBJECTS; 3. BLOTTING PAPER FOR REMOVING SUPERFLUOUS WATER FROM THE SLIDES AND DRAWING FLUIDS UNDER THE cover glass; 4. pieces of elder or sunflower pith, for holding small objects while making sections. IN ADDITION TO THESE IMPLEMENTS, A FEW REAGENTS MAY BE RECOMMENDED FOR THE SIMPLER HISTOLOGICAL WORK. THE MOST IMPORTANT OF THESE ARE ALCOHOL, GLYCERINE, POTASH (A STRONG SOLUTION OF POTASSIUM HYDRATE IN WATER), IODINE (EITHER A LITTLE OF THE COMMERCIAL TINCTURE OF IODINE IN WATER, OR, BETTER, A SOLUTION OF IODINE IN IODIDE OF POTASSIUM), ACETIC ACID, AND some staining fluid. (An aqueous or alcoholic solution of gentian violet or methyl violet is one of the best.) A CAREFUL RECORD SHOULD BE KEPT BY THE STUDENT OF ALL WORK DONE, BOTH BY MEANS OF WRITTEN NOTES AND DRAWINGS. FOR MOST PURPOSES PENCIL DRAWINGS ARE MOST CONVENIENT, AND THESE SHOULD BE MADE WITH A MODERATELY SOFT PENCIL ON UNRULED PAPER. IF IT IS DESIRED TO MAKE THE DRAWINGS WITH INK, A CAREFUL OUTLINE SHOULD FIRST BE MADE WITH A HARD PENCIL AND THIS INKED OVER WITH INDIA-INK OR BLACK DRAWING INK. INK DRAWINGS ARE BEST MADE UPON LIGHT BRISTOL BOARD WITH A hard, smooth-finished surface. WHEN OBTAINABLE, THE STUDENT WILL DO BEST TO WORK WITH FRESHLY GATHERED SPECIMENS; BUT AS THESE ARE NOT ALWAYS TO be had when wanted, a few words about gathering and preserving material may be of service. MOST OF THE LOWER GREEN PLANTS ( algæ) MAY BE KEPT FOR A LONG TIME IN GLASS JARS OR OTHER VESSELS, PROVIDED CARE IS TAKEN TO REMOVE ALL DEAD SPECIMENS AT FIRST AND TO RENEW THE WATER FROM TIME TO TIME. THEY USUALLY THRIVE BEST IN A NORTH window where they get little or no direct sunshine, and it is well to avoid keeping them too warm. NUMBERS OF THE MOST VALUABLE FUNGI— i.e. THE LOWER PLANTS THAT ARE NOT GREEN—GROW SPONTANEOUSLY ON MANY organic SUBSTANCES THAT ARE KEPT WARM AND MOIST. FRESH BREAD KEPT MOIST AND COVERED WITH A GLASS WILL IN A SHORT TIME PRODUCE A VARIED CROP OF MOULDS, AND FRESH HORSE MANURE KEPT IN THE SAME WAY SERVES TO SUPPORT A STILL GREATER NUMBER of fungi. MOSSES, FERNS, ETC., CAN BE RAISED WITH A LITTLE CARE, AND OF COURSE VERY MANY FLOWERING PLANTS ARE READILY GROWN IN pots. MOST OF THE SMALLER PARASITIC FUNGI (RUSTS, MILDEWS, ETC.) MAY BE KEPT DRY FOR ANY LENGTH OF TIME, AND ON MOISTENING with a weak solution of caustic potash will serve nearly as well as freshly gathered specimens for most purposes. WHEN IT IS DESIRED TO PRESERVE AS PERFECTLY AS POSSIBLE THE MORE DELICATE PLANT STRUCTURES FOR FUTURE STUDY, STRONG ALCOHOL IS THE BEST AND MOST CONVENIENT PRESERVING AGENT. EXCEPT FOR LOSS OF COLOR IT PRESERVES NEARLY ALL PLANT TISSUES perfectly. CHAPTER II. THE CELL. IF WE MAKE A THIN SLICE ACROSS THE STEM OF A RAPIDLY GROWING PLANT,— e.g. GERANIUM, BEGONIA, CELERY,—MOUNT IT IN WATER, AND EXAMINE IT MICROSCOPICALLY, IT WILL BE FOUND TO BE MADE UP OF NUMEROUS CAVITIES OR CHAMBERS SEPARATED BY DELICATE PARTITIONS. OFTEN THESE CAVITIES ARE OF SUFFICIENT SIZE TO BE VISIBLE TO THE NAKED EYE, AND EXAMINED WITH A HAND LENS THE SECTION APPEARS LIKE A PIECE OF FINE LACE, EACH MESH BEING ONE OF THE CHAMBERS VISIBLE WHEN MORE STRONGLY magnified. These chambers are known as “cells,” and of them the whole plant is built up. In order to study the structure of the cell more exactly we will select such as may be examined without cutting them. A good example is furnished by the common spiderwort (Fig. 1). Attached to the base of the stamens (Fig. 85, B) are delicate hairs composed of chains of cells, which may be examined alive by carefully removing a stamen and placing it in a drop of water under a cover glass. Each cell (Fig. 1) is an oblong sac, with a delicate colorless wall which chemical tests show to be composed of cellulose, a substance closely resembling starch. Within this sac, and forming a lining to it, is a thin layer of colorless matter containing many fine granules. Bands and threads of the same substance traverse the cavity of the cell, which is filled with a deep purple homogeneous fluid. This fluid, which in most cells is colorless, is called the cell sap, and is composed mainly of water. Imbedded in the granular lining of the sac is a roundish body (n), which itself has a definite membrane, and usually shows one or more roundish bodies within, besides an indistinctly granular appearance. This body is called the nucleus of the cell, and the small one within it, the nucleolus. The membrane surrounding the cell is known as the cell wall, and in young plant cells is always composed of cellulose. The granular substance lining the cell wall (Fig. 1, pr.) is called “protoplasm,” and with the nucleus constitutes the living part of the cell. If sufficiently magnified, the granules within the protoplasm will be seen to be in active streaming motion. This movement, which is very evident here, is not often so conspicuous, but still may often be detected without difficulty. [1] [Page 4] [Page 5] [Page 6] [Page 7] Fig. 1.—A single cell from a hair on the stamen of the common spiderwort (Tradescantia), × 150. pr. protoplasm; w, cell wall; n, nucleus. Fig. 2. Fig. 2.—An Amœba. A cell without a cell wall. n, nucleus; v, vacuoles, × 300. THE CELL MAY BE REGARDED AS THE UNIT OF ORGANIC STRUCTURE, AND OF CELLS ARE BUILT UP ALL OF THE COMPLICATED STRUCTURES OF WHICH THE BODIES OF THE HIGHEST PLANTS AND ANIMALS ARE COMPOSED. WE SHALL FIND THAT THE CELLS MAY BECOME VERY MUCH MODIFIED FOR VARIOUS PURPOSES, BUT AT FIRST THEY ARE ALMOST IDENTICAL IN STRUCTURE, AND ESSENTIALLY THE SAME AS THE ONE WE have just considered. Fig. 3. Fig. 3.—Hairs from the leaf stalk of a wild geranium. A, single- celled hair. B and C, hairs consisting of a row of cells. The terminal rounded cell secretes a peculiar scented oil that gives the plant its characteristic odor. B, × 50; C, × 150. VERY MANY OF THE LOWER FORMS OF LIFE CONSIST OF BUT A SINGLE CELL WHICH MAY OCCASIONALLY BE DESTITUTE OF A CELL WALL. SUCH A FORM IS SHOWN IN FIGURE 2. HERE WE HAVE A MASS OF PROTOPLASM WITH A NUCLEUS ( n) AND CAVITIES (VACUOLES, v) FILLED WITH CELL SAP, BUT NO CELL WALL. THE PROTOPLASM IS IN CONSTANT MOVEMENT, AND BY EXTENSIONS OF A PORTION OF THE MASS AND CONTRACTION OF OTHER PARTS, THE WHOLE CREEPS SLOWLY ALONG. OTHER NAKED CELLS ( Fig. 12, B; FIG. 16, C) ARE PROVIDED WITH DELICATE THREAD-LIKE PROCESSES OF PROTOPLASM CALLED “CILIA” (SING. cilium), WHICH ARE IN ACTIVE VIBRATION, AND PROPEL the cell through the water. [Page 8] Fig. 4. Fig. 4.—A, cross section. B, longitudinal section of the leaf stalk of wild geranium, showing its cellular structure. Ep. epidermis. h, a hair, × 50. C, a cell from the prothallium (young plant) of a fern, × 150. The contents of the cell contracted by the action of a solution of sugar. On placing a cell into a fluid denser than the cell sap (e.g. a ten-per-cent solution of sugar in water), a portion of the water will be extracted from the cell, and we shall then see the protoplasm receding from the wall (Fig. 4, C), showing that it is normally in a state of tension due to pressure from within of the cell sap. The cell wall shows the same thing though in a less degree, owing to its being much more rigid than the protoplasmic lining. It is owing to the partial collapsing of the cells, consequent on loss of water, that plants wither when the supply of water is cut off. AS CELLS GROW, NEW ONES ARE FORMED IN VARIOUS WAYS. IF THE NEW CELLS REMAIN TOGETHER, CELL AGGREGATES, CALLED TISSUES, ARE PRODUCED, AND OF THESE TISSUES ARE BUILT UP THE VARIOUS ORGANS OF THE HIGHER PLANTS. THE SIMPLEST TISSUES ARE ROWS OF CELLS, SUCH AS FORM THE HAIRS COVERING THE SURFACE OF THE ORGANS OF MANY FLOWERING PLANTS ( Fig. 3), AND ARE DUE TO A DIVISION OF THE CELLS IN A SINGLE DIRECTION. IF THE DIVISIONS TAKE PLACE IN THREE PLANES, MASSES OF CELLS, SUCH AS MAKE UP the stems, etc., of the higher plants, result (Fig. 4, A, B). CHAPTER III. CLASSIFICATION OF PLANTS.—PROTOPHYTES. FOR THE SAKE OF CONVENIENCE IT IS DESIRABLE TO COLLECT INTO GROUPS SUCH PLANTS AS ARE EVIDENTLY RELATED; BUT AS OUR KNOWLEDGE OF MANY FORMS IS STILL VERY IMPERFECT, ANY CLASSIFICATION WE MAY ADOPT MUST BE TO A GREAT EXTENT ONLY provisional, and subject to change at any time, as new forms are discovered or others become better understood. THE FOLLOWING GENERAL DIVISIONS ARE USUALLY ACCEPTED: I. SUB-KINGDOM (OR BRANCH); II. CLASS; III. ORDER; IV. Family; V. Genus; VI. Species. TO ILLUSTRATE: THE WHITE PINE BELONGS TO THE HIGHEST GREAT DIVISION (SUB-KINGDOM) OF THE PLANT KINGDOM. THE PLANTS OF THIS DIVISION ALL PRODUCE SEEDS, AND HENCE ARE CALLED “SPERMAPHYTES” (“SEED PLANTS”). THEY MAY BE DIVIDED INTO TWO GROUPS (CLASSES), DISTINGUISHED BY CERTAIN PECULIARITIES IN THE FLOWERS AND SEEDS. THESE ARE NAMED RESPECTIVELY “GYMNOSPERMS” AND “ANGIOSPERMS,” AND TO THE FIRST OUR PLANT BELONGS. THE GYMNOSPERMS MAY BE FURTHER DIVIDED INTO SEVERAL SUBORDINATE GROUPS (ORDERS), ONE OF WHICH, THE CONIFERS, OR CONE-BEARING EVERGREENS, INCLUDES OUR PLANT. THIS ORDER INCLUDES SEVERAL FAMILIES, AMONG THEM THE FIR FAMILY ( Abietineæ), INCLUDING THE PINES AND FIRS. OF THE SUB-DIVISIONS (genera, SING. genus) OF THE FIR FAMILY, ONE OF THE MOST FAMILIAR IS THE GENUS Pinus, WHICH EMBRACES ALL THE TRUE PINES. COMPARING DIFFERENT KINDS OF PINES, WE FIND THAT THEY DIFFER IN THE FORM OF THE CONES, ARRANGEMENT OF THE LEAVES, AND OTHER MINOR PARTICULARS. THE FORM WE HAVE SELECTED DIFFERS FROM ALL OTHER NATIVE FORMS IN ITS CONES, AND ALSO IN HAVING THE LEAVES IN FIVES, INSTEAD OF TWOS OR THREES, AS IN MOST OTHER KINDS. THEREFORE TO DISTINGUISH THE WHITE PINE FROM ALL OTHER pines, it is given a “specific” name, strobus. [Page 9] The following table will show more plainly what is meant: Sub-kingdom, Spermaphyta. Includes all spermaphytes, or seed plants. Class, Gymnospermæ. All naked-seeded plants. Order, Coniferæ. All cone-bearing evergreens. Family, Abietineæ. Firs, Pines, etc. Genus, Pinus. Pines. Species, Strobus. White Pine. SUB-KINGDOM I. PROTOPHYTES. THE NAME PROTOPHYTES (Protophyta) HAS BEEN APPLIED TO A LARGE NUMBER OF SIMPLE PLANTS, WHICH DIFFER A GOOD DEAL AMONG THEMSELVES. SOME OF THEM DIFFER STRIKINGLY FROM THE HIGHER PLANTS, AND RESEMBLE SO REMARKABLY CERTAIN LOW FORMS OF ANIMAL LIFE AS TO BE QUITE INDISTINGUISHABLE FROM THEM, AT LEAST IN CERTAIN STAGES. INDEED, THERE ARE CERTAIN FORMS THAT ARE QUITE AS MUCH ANIMAL AS VEGETABLE IN THEIR ATTRIBUTES, AND MUST BE REGARDED AS CONNECTING THE TWO KINGDOMS. Such forms are the slime moulds (Fig. 5), Euglena (Fig. 9), Volvox (Fig. 10), and others. Fig. 5. Fig. 5.—A, a portion of a slime mould growing on a bit of rotten wood, × 3. B, outline of a part of the same, × 25. C, a small portion showing the densely granular character of the protoplasm, × 150. D, [Page 10] [Page 11] [Page 12] a group of spore cases of a slime mould (Trichia), of about the natural size. E, two spore cases, × 5. The one at the right has begun to open. F, a thread (capillitium) and spores of Trichia, × 50. G, spores. H, end of the thread, × 300. I, zoöspores of Trichia, × 300. i, ciliated form; ii, amœboid forms. n, nucleus. v, contractile vacuole. J, K, sporangia of two common slime moulds. J, Stemonitis, × 2. K, Arcyria, × 4. OTHER PROTOPHYTES, WHILE EVIDENTLY ENOUGH OF VEGETABLE NATURE, ARE NEVERTHELESS VERY DIFFERENT IN SOME RESPECTS from the higher plants. THE PROTOPHYTES MAY BE DIVIDED INTO THREE CLASSES: I. THE SLIME MOULDS ( Myxomycetes); II. THE SCHIZOPHYTES; III. The green monads (Volvocineæ). CLASS I.—THE SLIME MOULDS. These curious organisms are among the most puzzling forms with which the botanist has to do, as they are so much LIKE SOME OF THE LOWEST FORMS OF ANIMAL LIFE AS TO BE SCARCELY DISTINGUISHABLE FROM THEM, AND INDEED THEY ARE SOMETIMES REGARDED AS ANIMALS RATHER THAN PLANTS. AT CERTAIN STAGES THEY CONSIST OF NAKED MASSES OF PROTOPLASM OF VERY CONSIDERABLE SIZE, NOT INFREQUENTLY SEVERAL CENTIMETRES IN DIAMETER. THESE ARE MET WITH ON DECAYING LOGS IN DAMP WOODS, ON ROTTING LEAVES, AND OTHER DECAYING VEGETABLE MATTER. THE COMMONEST ONES ARE BRIGHT YELLOW OR WHITISH, AND FORM SOFT, slimy coverings over the substratum (Fig. 5, A), PENETRATING INTO ITS CREVICES AND SHOWING SENSITIVENESS TOWARD LIGHT. THE PLASMODIUM, AS THE MASS OF PROTOPLASM IS CALLED, MAY BE MADE TO CREEP UPON A SLIDE IN THE FOLLOWING WAY: A TUMBLER IS FILLED WITH WATER AND PLACED IN A SAUCER FILLED WITH SAND. A STRIP OF BLOTTING PAPER ABOUT THE WIDTH OF THE SLIDE IS NOW PLACED WITH ONE END IN THE WATER, THE OTHER HANGING OVER THE EDGE OF THE GLASS AND AGAINST ONE SIDE OF A SLIDE, WHICH IS THUS HELD UPRIGHT, BUT MUST NOT BE ALLOWED TO TOUCH THE SIDE OF THE TUMBLER. THE STRIP OF BLOTTING PAPER SUCKS UP THE WATER, WHICH FLOWS SLOWLY DOWN THE SURFACE OF THE SLIDE IN CONTACT WITH THE BLOTTING PAPER. IF NOW A BIT OF THE SUBSTANCE UPON WHICH THE PLASMODIUM IS GROWING IS PLACED AGAINST THE BOTTOM OF THE SLIDE ON THE SIDE WHERE THE STREAM OF WATER IS, THE PROTOPLASM WILL CREEP UP AGAINST THE CURRENT OF WATER AND SPREAD OVER THE SLIDE, FORMING DELICATE THREADS IN WHICH MOST ACTIVE STREAMING MOVEMENTS OF THE CENTRAL GRANULAR PROTOPLASM MAY BE SEEN UNDER THE MICROSCOPE, AND THE ENDS OF THE BRANCHES MAY BE SEEN TO PUSH FORWARD MUCH AS WE SAW IN THE AMŒBA. IN ORDER THAT THE EXPERIMENT MAY BE SUCCESSFUL, THE WHOLE APPARATUS SHOULD BE CAREFULLY PROTECTED FROM THE LIGHT, AND ALLOWED TO STAND FOR SEVERAL HOURS. THIS POWER OF MOVEMENT, AS WELL AS THE POWER TO TAKE IN SOLID FOOD, ARE EMINENTLY ANIMAL CHARACTERISTICS, THOUGH THE former is common to many plants as well. AFTER A LONGER OR SHORTER TIME THE MASS OF PROTOPLASM CONTRACTS AND GATHERS INTO LITTLE HEAPS, EACH OF WHICH DEVELOPS INTO A STRUCTURE THAT HAS NO RESEMBLANCE TO ANY ANIMAL, BUT WOULD BE AT ONCE PLACED WITH PLANTS. IN ONE COMMON FORM (Trichia) THESE ARE ROUND OR PEAR-SHAPED BODIES OF A YELLOW COLOR, AND ABOUT AS BIG AS A PIN HEAD (Fig. 5, D), OCCURRING IN GROUPS ON ROTTEN LOGS IN DAMP WOODS. OTHERS ARE STALKED ( Arcyria, Stemonitis) (Fig. 5, J, K), AND OF VARIOUS COLORS,—RED, BROWN, ETC. THE OUTER PART OF THE STRUCTURE IS A MORE OR LESS FIRM WALL, WHICH BREAKS WHEN ripe, discharging a powdery mass, mixed in most forms with very fine fibres. When strongly magnified the fine dust is found to be made up of innumerable small cells with thick walls, marked with ridges or processes which differ much in different species. The fibres also differ much in different genera. Sometimes they are simple, hair-like threads; in others they are hollow tubes with spiral thickenings, often very regularly placed, running around their walls. The spores may sometimes be made to germinate by placing them in a drop of water, and allowing them to remain in a warm place for about twenty-four hours. If the experiment has been successful, at the end of this time the spore membrane will have burst, and the contents escaped in the form of a naked mass of protoplasm (Zoöspore) with a nucleus, and often showing a vacuole (Fig. 5, v), that alternately becomes much distended, and then disappears entirely. On first escaping it is usually provided with a long, whip-like filament of protoplasm, which is in active movement, and by means of which the cell swims actively through the water (Fig. 5, I i). Sometimes such a cell will be seen to divide into two, the process taking but a short time, so that the numbers of these cells under favorable conditions may become very large. After a time the lash is withdrawn, and the cell assumes much the form of a small amœba (I ii). THE SUCCEEDING STAGES ARE DIFFICULT TO FOLLOW. AFTER REPEATEDLY DIVIDING, A LARGE NUMBER OF THESE AMŒBA-LIKE CELLS RUN TOGETHER, COALESCING WHEN THEY COME IN CONTACT, AND FORMING A MASS OF PROTOPLASM THAT GROWS, AND FINALLY ASSUMES the form from which it started. Of the common forms of slime moulds the species of Trichia (Figs. D, I) and Physarum are, perhaps, the best for studying the germination, as the spores are larger than in most other forms, and germinate more readily. The experiment is apt to be most successful if the spores are sown in a drop of water in which has been infused some vegetable matter, such as a bit of rotten wood, boiling thoroughly to kill all germs. A drop of this fluid should be placed on a perfectly clean cover glass, which it is well to pass once or twice through a flame, and the spores transferred to this drop with a needle previously heated. By these precautions foreign germs will be avoided, which otherwise may interfere seriously with the growth of the young slime moulds. After sowing the spores in the drop of culture fluid, the whole should be inverted over a so-called “moist chamber.” This is simply a square of thick blotting paper, in which an opening is cut small enough to be entirely covered by the cover glass, but large enough so that the drop in the centre of the cover glass will not touch the sides of the chamber, but will hang suspended clear in it. The blotting paper should be soaked thoroughly in pure water (distilled water is preferable), and then placed on a slide, covering carefully with the cover glass with the suspended drop of fluid containing the spores. The whole should be kept under cover so as to prevent loss of water by evaporation. By this method the spores may be examined conveniently without disturbing them, and the whole may be kept as long as desired, so long as the blotting paper is kept wet, so as to prevent the suspended drop from drying up. CLASS II.—Schizophytes. [Page 13] [Page 14] THE SCHIZOPHYTES ARE VERY SMALL PLANTS, THOUGH NOT INFREQUENTLY OCCURRING IN MASSES OF CONSIDERABLE SIZE. THEY ARE AMONG THE COMMONEST OF ALL PLANTS, AND ARE FOUND EVERYWHERE. THEY MULTIPLY ALMOST ENTIRELY BY SIMPLE TRANSVERSE DIVISION, OR SPLITTING OF THE CELLS, WHENCE THEIR NAME. THERE ARE TWO PRETTY WELL-MARKED ORDERS,—THE BLUE-GREEN SLIMES (Cyanophyceæ) AND THE BACTERIA ( Schizomycetes). THEY ARE DISTINGUISHED, PRIMARILY, BY THE FIRST (WITH A VERY FEW exceptions) containing chlorophyll (leaf-green), which is entirely absent from nearly all of the latter. THE BLUE-GREEN SLIMES: THESE ARE, WITH FEW EXCEPTIONS, GREEN PLANTS OF SIMPLE STRUCTURE, BUT POSSESSING, IN ADDITION TO THE ORDINARY GREEN PIGMENT (CHLOROPHYLL, OR LEAF-GREEN), ANOTHER COLORING MATTER, SOLUBLE IN WATER, AND USUALLY BLUE IN color, though sometimes yellowish or red. Fig. 6. Fig. 6.—Blue-green slime (Oscillaria) . A, mass of filaments of the natural size. B, single filament, × 300. C, a piece of a filament that has become separated. s, sheath, × 300. AS A REPRESENTATIVE OF THE GROUP, WE WILL SELECT ONE OF THE COMMONEST FORMS ( Oscillaria), KNOWN SOMETIMES AS GREEN SLIME, FROM FORMING A DARK BLUE-GREEN OR BLACKISH SLIMY COAT OVER THE MUD AT THE BOTTOM OF STAGNANT OR SLUGGISH WATER, IN WATERING TROUGHS, ON DAMP ROCKS, OR EVEN ON MOIST EARTH. A SEARCH IN THE PLACES MENTIONED CAN HARDLY FAIL TO SECURE PLENTY OF SPECIMENS FOR STUDY. IF A BIT OF THE SLIMY MASS IS TRANSFERRED TO A CHINA DISH, OR PLACED WITH CONSIDERABLE WATER ON A PIECE OF STIFF PAPER, AFTER A SHORT TIME THE EDGE OF THE MASS WILL SHOW NUMEROUS EXTREMELY FINE FILAMENTS OF A DARK BLUE-GREEN COLOR, RADIATING IN ALL DIRECTIONS FROM THE MASS ( FIG. 6, a). THE FILAMENTS ARE THE INDIVIDUAL PLANTS, AND POSSESS CONSIDERABLE POWER OF MOTION, AS IS SHOWN BY LETTING THE MASS REMAIN UNDISTURBED FOR A DAY OR TWO, AT THE END OF WHICH TIME THEY WILL HAVE FORMED A THIN FILM OVER THE SURFACE OF THE VESSEL IN WHICH THEY ARE KEPT; AND THE RADIATING arrangement of the filaments can then be plainly seen. IF THE MASS IS ALLOWED TO DRY ON THE PAPER, IT OFTEN LEAVES A BRIGHT BLUE STAIN, DUE TO THE BLUE PIGMENT IN THE CELLS OF THE FILAMENT. THIS BLUE COLOR CAN ALSO BE EXTRACTED BY PULVERIZING A QUANTITY OF THE DRIED PLANTS, AND POURING WATER OVER THEM, THE WATER SOON BECOMING TINGED WITH A DECIDED BLUE. IF NOW THE WATER CONTAINING THE BLUE PIGMENT IS FILTERED, AND the residue treated with alcohol, the latter will extract the chlorophyll, becoming colored of a yellow-green. The microscope shows that the filaments of which the mass is composed (Fig. 6, B) are single rows of short cylindrical cells of uniform diameter, except at the end of the filament, where they usually become somewhat smaller, so that the tip is more or less distinctly pointed. The protoplasm of the cells has a few small granules scattered through it, and is colored uniformly of a pale blue-green. No nucleus can be seen. If the filament is broken, there may generally be detected a delicate, colorless sheath that surrounds it, and extends beyond the end cells (Fig. 6, c). The filament increases in length by the individual cells undergoing division, this always taking place at right angles to the axis of the filament. New filaments are produced simply by the older ones breaking into a number of pieces, each of which rapidly grows to full size. THE NAME “OSCILLARIA” ARISES FROM THE PECULIAR OSCILLATING OR SWINGING MOVEMENTS THAT THE PLANT EXHIBITS. THE MOST marked movement is a swaying from side to side, combined with a rotary motion of the free ends of the filaments, which ARE OFTEN TWISTED TOGETHER LIKE THE STRANDS OF A ROPE. IF THE FILAMENTS ARE ENTIRELY FREE, THEY MAY OFTEN BE OBSERVED TO move forward with a slow, creeping movement. Just how these movements are caused is still a matter of controversy. THE LOWEST OF THE Cyanophyceæ ARE STRICTLY SINGLE-CELLED, SEPARATING AS SOON AS FORMED, BUT COHERING USUALLY IN masses or colonies by means of a thick mucilaginous substance that surrounds them (Fig. 7, D). THE HIGHER ONES ARE FILAMENTS, IN WHICH THERE MAY BE CONSIDERABLE DIFFERENTIATION. THESE OFTEN OCCUR IN MASSES OF CONSIDERABLE SIZE, FORMING JELLY-LIKE LUMPS, WHICH MAY BE SOFT OR QUITE FIRM ( Fig. 7, A, B). THEY ARE SOMETIMES FOUND ON DAMP GROUND, BUT MORE COMMONLY ATTACHED TO PLANTS, STONES, ETC., IN WATER. THE MASSES VARY IN COLOR FROM LIGHT BROWN to deep blackish green, and in size from that of a pin head to several centimetres in diameter. [Page 15] [Page 16] [Page 17] Fig. 8. Fig. 8.—Bacteria. Fig. 7. Fig. 7.—Forms of Cyanophyceæ. A, Nostoc. B, Glœotrichia, × 1. C, individual of Glœotrichia. D, Chroöcoccus. E, Nostoc. F, Oscillaria. G, H, Tolypothrix. All × 300. y, heterocyst. sp. spore. IN THE HIGHER FORMS SPECIAL CELLS CALLED HETEROCYSTS ARE FOUND. THEY ARE COLORLESS, OR LIGHT YELLOWISH, REGULARLY DISPOSED; BUT THEIR FUNCTION IS NOT KNOWN. BESIDES THESE, CERTAIN CELLS BECOME THICK-WALLED, AND FORM RESTING CELLS (SPORES) FOR THE PROPAGATION OF THE PLANT ( FIG. 7, C. sp.). IN SPECIES WHERE THE SHEATH OF THE FILAMENT IS WELL MARKED (Fig. 7, H), groups of cells slip out of the sheath, and develop a new one, thus giving rise to a new plant. The bacteria (Schizomycetes), ALTHOUGH AMONG THE COMMONEST OF ORGANISMS, OWING TO THEIR EXCESSIVE MINUTENESS, ARE DIFFICULT TO STUDY, ESPECIALLY FOR THE BEGINNER. THEY RESEMBLE, IN THEIR GENERAL STRUCTURE AND METHODS OF REPRODUCTION, THE BLUE-GREEN SLIMES, BUT ARE, WITH VERY FEW EXCEPTIONS, DESTITUTE OF CHLOROPHYLL, ALTHOUGH OFTEN POSSESSING BRIGHT PIGMENTS,—BLUE, VIOLET, RED, ETC. IT IS ONE OF THESE THAT SOMETIMES FORMS BLOOD-RED SPOTS IN FLOUR PASTE OR BITS OF BREAD THAT HAVE BEEN KEPT VERY MOIST AND WARM. THEY ARE UNIVERSALLY PRESENT WHERE DECOMPOSITION IS GOING ON, AND ARE THEMSELVES THE PRINCIPAL AGENTS OF DECAY, WHICH IS THE RESULT OF THEIR FEEDING UPON THE SUBSTANCE, AS, LIKE ALL PLANTS WITHOUT CHLOROPHYLL, THEY REQUIRE ORGANIC MATTER FOR FOOD. MOST OF THE SPECIES ARE VERY TENACIOUS OF LIFE, AND MAY BE COMPLETELY DRIED UP FOR A LONG TIME WITHOUT DYING, AND ON BEING PLACED IN WATER WILL QUICKLY REVIVE. BEING SO EXTREMELY SMALL, THEY ARE READILY CARRIED ABOUT IN THE AIR IN THEIR DRIED-UP CONDITION, AND THUS FALL UPON EXPOSED BODIES, SETTING UP decomposition if the conditions are favorable. A SIMPLE EXPERIMENT TO SHOW THIS MAY BE PERFORMED BY TAKING TWO TEST TUBES and partly filling them with an infusion of almost any organic substance (dried leaves OR HAY, OR A BIT OF MEAT WILL ANSWER). THE FLUID SHOULD NOW BE BOILED SO AS TO KILL ANY GERMS THAT MAY BE IN IT; AND WHILE HOT, ONE OF THE VESSELS SHOULD BE SECURELY STOPPED UP WITH A PLUG OF COTTON WOOL, AND THE OTHER LEFT OPEN. THE COTTON PREVENTS ACCESS OF ALL SOLID PARTICLES, BUT ALLOWS THE AIR TO ENTER. IF PROPER CARE HAS BEEN TAKEN, THE INFUSION IN THE CLOSED VESSEL WILL REMAIN UNCHANGED INDEFINITELY; BUT THE OTHER WILL SOON BECOME TURBID, AND A DISAGREEABLE ODOR WILL BE GIVEN OFF. MICROSCOPIC EXAMINATION SHOWS THE FIRST TO BE FREE FROM GERMS OF ANY KIND, WHILE the second is swarming with various forms of bacteria. THESE LITTLE ORGANISMS HAVE OF LATE YEARS ATTRACTED THE ATTENTION OF VERY MANY scientists, from the fact that to them is due many, if not all, contagious diseases. The GERMS OF MANY SUCH DISEASES HAVE BEEN ISOLATED, AND EXPERIMENTS PROVE BEYOND doubt that these are alone the causes of the diseases in question. If a drop of water containing bacteria is examined, we find them to be excessively small, many of them barely visible with the strongest lenses. The larger ones (Fig. 8) recall quite strongly the smaller species of oscillaria, and exhibit similar movements. Others are so small as to appear as mere lines and dots, even with the strongest lenses. Among the common forms are small, nearly globular cells; oblong, rod-shaped or thread-shaped filaments, either straight or curved, or even spirally twisted. Frequently they show a quick movement which is probably in all cases due to cilia, which are, however, too small to be seen in most cases. [Page 18] [Page 19] Fig. 10. Fig. 10.—Volvox. A, mature colony, containing several smaller ones (x), × 50. B, Two cells showing the cilia, × 300. Fig. 9. Fig. 9.—Euglena. A, individual in the active condition. E, the red “eye- spot.” c, flagellum. n, nucleus. B, resting stage. C, individual dividing, × 300. REPRODUCTION IS FOR THE MOST PART BY SIMPLE TRANSVERSE DIVISION, AS IN OSCILLARIA; BUT OCCASIONALLY SPORES ARE produced also. CLASS III.—GREEN MONADS (Volvocineæ). THIS GROUP OF THE PROTOPHYTES IS UNQUESTIONABLY CLOSELY RELATED TO CERTAIN LOW ANIMALS ( Monads OR Flagellata), WITH WHICH THEY ARE SOMETIMES UNITED. THEY ARE CHARACTERIZED BY BEING ACTIVELY MOTILE, AND ARE EITHER STRICTLY UNICELLULAR, or the cells are united by a gelatinous envelope into a colony of definite form. Of the first group, Euglena (Fig. 9), may be selected as a type. This organism is found frequently among other algæ, and occasionally forms a green film on stagnant water. It is sometimes regarded as a plant, sometimes as an animal, and is an elongated, somewhat worm-like cell without a definite cell wall, so that it can change its form to some extent. The protoplasm contains oval masses, which are bright green in color; but the forward pointed end of the cell is colorless, and has a little depression. At this end there is a long vibratile protoplasmic filament (c), by means of which the cell moves. There is also to be seen near this end a red speck (e) which is probably sensitive to light. A nucleus can usually be seen if the cell is first killed with an iodine solution, which often will render the flagellum (c) more evident, this being invisible while the cell is in motion. The cells multiply by division. Previous to this the flagellum is withdrawn, and a firm cell wall is formed about the cell (Fig. 9, B). The contents then divide into two or more parts, which afterwards escape as new individuals. OF THE FORMS THAT ARE UNITED IN COLONIES ONE OF THE BEST KNOWN IS Volvox (FIG. 10). THIS PLANT IS SOMETIMES FOUND IN QUIET WATER, WHERE IT FLOATS ON OR NEAR THE SURFACE AS A DARK GREEN BALL, JUST LARGE ENOUGH TO BE SEEN WITH THE NAKED EYE. THEY MAY BE KEPT FOR SOME TIME IN AQUARIA, AND WILL SOMETIMES MULTIPLY RAPIDLY, BUT ARE VERY SUSCEPTIBLE TO EXTREMES OF temperature, especially of heat. The colony (Fig. 10, A) is a hollow sphere, the numerous green cells of which it is composed forming a single layer on the outside. By killing with iodine, and using a strong lens, each cell is seen to be somewhat pear-shaped (Fig. B), with the pointed end out. Attached to this end are two vibratile filaments (cilia or flagella), and the united movements of these cause the rolling motion of the whole colony. Usually a number of young colonies (Fig. x) are found within the mother colony. These arise by the repeated bipartition of a single cell, and escape finally, forming independent colonies. Another (sexual) form of reproduction occurs, similar to that found in many higher plants; but as it only occurs at certain seasons, it is not likely to be met with by the student. OTHER FORMS RELATED TO Volvox, AND SOMETIMES MET WITH, ARE Gonium, IN WHICH THERE ARE SIXTEEN CELLS, FORMING A FLAT SQUARE; Pandorina AND Eudorina, WITH SIXTEEN CELLS, FORMING AN OVAL OR GLOBULAR COLONY LIKE Volvox, BUT MUCH smaller. In all of these the structure of the cells is essentially as in Volvox. CHAPTER IV. SUB-KINGDOM II. ALGÆ. IN THE SECOND SUB-KINGDOM OF PLANTS IS EMBRACED AN ENORMOUS ASSEMBLAGE OF PLANTS, DIFFERING WIDELY IN SIZE AND COMPLEXITY, AND YET SHOWING A SUFFICIENTLY COMPLETE GRADATION FROM THE LOWEST TO THE HIGHEST AS TO MAKE IT IMPRACTICABLE [Page 20] [2] [Page 21] [3] TO MAKE MORE THAN ONE SUB-KINGDOM TO INCLUDE THEM. THEY ARE NEARLY ALL AQUATIC FORMS, ALTHOUGH MANY OF THEM WILL survive long periods of drying, such forms occurring on moist earth, rocks, or the trunks of trees, but only growing when there is a plentiful supply of water. ALL OF THEM POSSESS CHLOROPHYLL, WHICH, HOWEVER, IN MANY FORMS, IS HIDDEN BY THE PRESENCE OF A BROWN OR RED PIGMENT. THEY ARE ORDINARILY DIVIDED INTO THREE CLASSES—I. THE GREEN ALGÆ ( Chlorophyceæ); II. BROWN ALGÆ (Phæophyceæ); III. Red Algæ (Rhodophyceæ). CLASS I.—GREEN ALGÆ. THE GREEN ALGÆ ARE TO BE FOUND ALMOST EVERYWHERE WHERE THERE IS MOISTURE, BUT ARE ESPECIALLY ABUNDANT IN SLUGGISH OR STAGNANT FRESH WATER, BEING MUCH LESS COMMON IN SALT WATER. THEY ARE FOR THE MOST PART PLANTS OF SIMPLE STRUCTURE, many being unicellular, and very few of them plants of large size. WE MAY RECOGNIZE FIVE WELL-MARKED ORDERS OF THE GREEN ALGÆ—I. GREEN SLIMES ( Protococcaceæ); II. Confervaceæ; III. Pond scums (Conjugatæ); IV. Siphoneæ; V. Stone-worts (Characeæ). ORDER I.—Protococcaceæ. THE MEMBERS OF THIS ORDER ARE MINUTE UNICELLULAR PLANTS, GROWING EITHER IN WATER OR ON THE DAMP SURFACES OF STONES, tree trunks, etc. The plants sometimes grow isolated, but usually the cells are united more or less regularly into colonies. A COMMON REPRESENTATIVE OF THE ORDER IS THE COMMON GREEN SLIME, Protococcus (FIG. 11, A, C), WHICH FORMS A DARK GREEN SLIMY COATING OVER STONES, TREE TRUNKS, FLOWER POTS, ETC. OWING TO THEIR MINUTE SIZE THE STRUCTURE CAN ONLY BE made out with the microscope. Fig. 11. Fig. 11.—Protococcaceæ. A, C, Protococcus. A, single cells. B, cells dividing by fission. C, successive steps in the process of internal cell division. In C iv, the young cells have mostly become free. D, a full-grown colony of Pediastrum. E, a young colony still surrounded by the membrane of the mother cell. F, Scenedesmus. All, × 300. G, small portion of a young colony of the water net (Hydrodictyon), × 150. Scraping off a little of the material mentioned into a drop of water upon a slide, and carefully separating it with needles, a cover glass may be placed over the preparation, and it is ready for examination. When magnified, the green film is found to be composed of minute globular cells of varying size, which may in places be found to be united into groups. With a higher power, each cell (Fig. 11, A) is seen to have a distinct cell wall, within which is colorless protoplasm. Careful examination shows that the chlorophyll is confined to several roundish bodies that are not usually in immediate contact with the wall of the cell. These green masses are called chlorophyll bodies (chloroplasts). Toward the centre of the cell, especially if it has first been treated with iodine, the nucleus may be found. The size of the cells, as well as the number of chloroplasts, varies a good deal. With a little hunting, specimens in various stages of division may be found. The division takes place in two ways. In the first (Fig. 11, B), known as fission, a wall is formed across the cell, dividing it into two cells, which may separate immediately or may remain united until they have undergone further division. In this case the original cell wall remains as part of the wall of the daughter cells. Fission is the commonest form of cell multiplication throughout the vegetable kingdom. The second form of cell division or internal cell division is shown at C. Here the protoplasm and nucleus repeatedly divide until a number of small cells are formed within the old one. These develop cell walls, and escape by the breaking of the old cell wall, which is left behind, and takes no part in the process. The cells thus formed are sometimes provided with two cilia, and are capable of active movement. Internal cell division, as we shall see, is found in most plants, but only at special times. Closely resembling Protococcus, and answering quite as well for study, are numerous aquatic forms, such as Chlorococcum (Fig. 12). These are for the most part destitute of a firm cell wall, but are imbedded in masses of gelatinous substance like many Cyanophyceæ. The chloroplasts are smaller and less distinct than in Protococcus. The cells are here oval rather than round, and often show a clear space at one end. Owing to the absence of a definite membrane, a distinction between fission and internal cell division can scarcely be made here. Often the cells escape from the gelatinous envelope, and swim actively by means of two cilia at the colorless end (Fig. 12, B). In this stage they closely resemble the individuals of a Volvox colony, or other green Flagellata, to which there is little doubt that they are related. [Page 22] [Page 23] Fig. 12. Fig. 12.—Chlorococcum, a plant related to Protococcus, but the naked cells are surrounded by a colorless gelatinous envelope. A, motionless cells. B, a cell that has escaped from its envelope and is ciliated, × 300. There are a number of curious forms common in fresh water that are probably related to Protococcus, but differ in having the cells united in colonies of definite form. Among the most striking are the different species of Pediastrum (Fig. 11, D, E), often met with in company with other algæ, and growing readily in aquaria when once established. They are of very elegant shapes, and the number of cells some multiple of four, usually sixteen. The cells form a flat disc, the outer ones being generally provided with a pair of spines. New individuals arise by internal division of the cells, the contents of each forming as many parts as there are cells in the whole colony. The young cells now escape through a cleft in the wall of the mother cell, but are still surrounded by a delicate membrane (Fig. 11, E). Within this membrane the young cells arrange themselves in the form of the original colony, and grow together, forming a new colony. A much larger but rarer form is the water net (Fig. 11, G), in which the colony has the form of a hollow net, the spaces being surrounded by long cylindrical cells placed end to end. Other common forms belong to the genus Scenedesmus (Fig. 11, F), of which there are many species. ORDER II.—Confervaceæ. UNDER THIS HEAD ARE INCLUDED A NUMBER OF FORMS OF WHICH THE SIMPLEST ONES APPROACH CLOSELY, ESPECIALLY IN THEIR YOUNGER STAGES, THE Protococcaceæ. INDEED, SOME OF THE SO-CALLED Protococcaceæ ARE KNOWN TO BE ONLY...