Contributors Number in parentheses indicate the pages on which the authors’ University of Minnesota Duluth, Ely, Minnesota contributions begin. 55731. Hedy Kling (117) Freshwater Institute, Winnipeg, Susan Carty (685) Department of Biology, Heidelberg Manitoba, Canada, R3T 2N6. College, Tiffin, Ohio 44883. J. P. Kociolek (559, 637, 655) Diatom Collection, Brec L. Clay (715) CH Diagnostic and Consulting California Academy of Sciences, Golden Gate Park, Service, Loveland, Colorado 80538. San Francisco, California 94118. Joseph F. Gerrath (353) Department of Botany, University of Guelph, Guelph, Ontario, Canada Jaroslava Komárková (117) Hydrobiological Institute, N1G 2W1. Academy of Sciences of the Czech Republic, Faculty of Biological Sciences, University of South Bohemia, David M. John (311) Department of Botany, The CZ-37005 Cˇeské Budeˇjovice, Czech Republic. Natural History Museum, London SW7 5BD, United Kingdom. Jirˇí Komárek (59, 117) Institute of Botany, Academy of Matthew L. Julius (559) Department of Biological Sciences of the Czech Republic, Faculty of Biological Sciences, St. Cloud State University, St. Cloud, Sciences, University of South Bohemia, CZ-37982 Minnesota 56301. Trˇebonˇ, Czech Republic. John C. Kingston (595) Center for Water and the Paul Kugrens (715) Department of Biology, Colorado Environment, Natural Resources Research Institute, State University, Fort Collins, Colorado 80523. xiii xiv Contributors Carole A. Lembi (805) Department of Botany and L. Elliot Shubert (253) Department of Botany, The Plant Pathology, Purdue University, West Lafayette, Natural History Museum, London SW7 5BD, Indiana 47907. United Kingdom. Rex L. Lowe (669) Biological Sciences, Bowling Green Peter A. Siver (523) Botany Department, Connecticut State University, Bowling Green, Ohio 43403 and College, New London, Connecticut, 06320. University of Michigan Biological Station, Pellston, John P. Smol (775) Department of Biology, Paleo- Michigan 49769. ecological Environmental Assessment and Research Laboratory (PEARL), Queen’s University, Kingston, Kenneth H. Nicholls(471, 511) S-15 Concession 1, RR Ontario, Canada K7L 3N6. #1 Sunderland, Ontario, Canada L0C 1H0. S. A. Spaulding (559, 637, 655) Diatom Collection, Hisayoshi Nozaki (225) Department of Biological California Academy of Sciences, Golden Gate Park, Sciences, Graduate School of Science, University of San Francisco, California 94118. Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. R. Jan Stevenson (775) Department of Zoology, Carla K. Oldham-Ott (423) Department of Biology, Michigan State University, East Lansing, Michigan, University of Akron, Akron, Ohio 44325. 48824. Donald W. Ott (423) Department of Biology, Eugene F. Stoermer (559) Michigan Herbarium University of Akron, Akron, Ohio 44325. University of Michigan, Ann Arbor, Michigan James R. Rosowski(383) School of Biological Sciences, 48109. College of Arts and Sciences, University of John D. Wehr (1, 11, 757) Louis Calder Center— Nebraska–Lincoln, Lincoln, Nebraska 68588. Biological Station and Department of Biological Sciences, Fordham University, Armonk, New York Robert G. Sheath (1, 11, 197) Office of Provost and 10504. Vice President for Academic Affairs, California State University, San Marcos, San Marcos, California Daniel E. Wujek (471) Department of Biology, Central 92096. Michigan University, Mt. Pleasant, Michigan 48859. Preface The study of freshwater algae in North America atics, biodiversity, or molecular biology. This is the has a long and rich history, with some of the early first book of its sort covering the entire continent. We monographic works dating back to the late 1800’s. In also hope that this book will serve to encourage new recent years, there has been an enormous and remark- generations of aquatic biologists to explore freshwater able level of research on this very diverse and hetero- algae carefully, rather than regarding phytoplankton geneous collection of organisms, making any definitive or benthic algae as simply quantities of chlorophyll or taxonomic or ecological treatise always out of date. carbon. The enormous variety of algae in lakes, rivers Nonetheless, it is our goal with this book to synthesize and other aquatic habitats is part of the ecological and update much of this vast knowledge, and to pro- content of aquatic communities, and their ecosystem vide a practical and comprehensive guide to all of the function varies with the species that occur there. genera of freshwater algae known from throughout Many of the previous monographs dealing with a the continent, in one volume. Chapters also provide broad geographic region are still useful, such as Smith’s guides to other publications and specialized works (1950) Freshwater Algae of the United States, but most for the identification and ecological information at the are decades old and do not contain recent taxonomic species level. Our intent is to combine the necessary changes. Our approach is to include chapters authored ecological and taxonomic information in a practical by experts who have specialized in the study of specific book that can be used by all scientists working in groups of freshwater algae. Given the great quantity of aquatic environments, whether their specialty is in research that has been produced on all of the major environmental monitoring, ecology, evolution, system- algal taxa, it is no longer possible for one or two xv xvi Preface authors to produce an authoritative book of this kind, Floyd, Paul Hamilton, Kyle Hoagland, Ronald Hoham, and one which will span the entire range of taxonomic Jeffrey Johansen, John Kingston, Dag Klaveness, Hedy and ecological detail that is now known about all Kling, Lothar Krienitz, Jorgen Kristiansen, Elsadore the organisms termed algae. This volume is modeled Kusel-Fetzmann, Carole Lembi, Rex Lowe, David closely after the book by Thorp and Covich on fresh- Mann, Richard McCourt, Øjvind Moestrup, Orlando water invertebrates (Ecology and Classification of Necchi Jr., Kenneth Nichols, Gianfranco Novarino, North American Freshwater Invertebrates), also pub- Hans Paerl, Russell Rhodes, Frank Round, Robert lished by Academic Press. Sheath, Alan Steinman, Eugene Stoermer, Francis The organization of this book includes an intro- Trainor, Richard Treimer, Herb Vandermeulen, Morgan duction to the freshwater algae (with a guide to the Vis, James Wee, John Wehr, Robert Wetzel, Ruth taxonomic chapters that follow), an overview of fresh- Willey, and David Williams. We wish to thank our water habitats, 20 taxonomic chapters, and finally editor at Academic Press, Dr. Charles R. Crumly, and chapters on the use of algae in environmental assess- his assistant, Ms. Christine Vogelei, for their continued ments and control of nuisance algae. More than 770 support throughout the creation and completion of this genera are described and illustrated in this book, and book. We also thank Ms. Geri Mattson at Mattson each taxonomic chapter includes an introduction to the Publishing Services for providing professional assis- key terms and characteristics of the group, ecological tance in the production of the final copy of the book. distribution, and a guide to the taxonomic literature We also wish to acknowledge the many colleagues who to distinguish species within each genus. While we have generously permitted reproduction of published and undoubtedly omitted some less common or yet un- unpublished material; these are acknowledged in the recorded freshwater genera, this compilation represents individual chapters. Kandis Elliot designed the beauti- an increase in the taxonomic scope and geographic fully illustrated cover. coverage of the freshwater algae of North America. The production of this book was partially supported This compares with roughly 490 genera recorded from by the Routh Endowment of the Louis Calder Center the United States by Smith (1950), about 335 in for JDW and NSERC grant number RGP 0105629 Prescott’s (1962) coverage of the Western Great Lakes to RGS, as well as general support from Fordham region, and nearly 380 genera from the southeastern University, University of Guelph and California State U.S. reported by Whitford and Schumacher (1984). University, San Marcos. Help in manuscript production Since not all algal groups are equally well studied, from Pam Anderson, Petra DelValle (Fordham), Marcy coverage in the present volume varies among taxa and Boyle (California State University, San Marcos), chapters. We hope that students, scientists working and Toni Pellizzari (Guelph) is appreciated. Lastly, we in water management agencies, and experienced phy- would like to thank our spouses, Deb Donaldson cologists will use this book thoroughly and provide us (Wehr) and Mary Koske (Sheath) for their understand- with feedback, such as missing taxa or incomplete geo- ing and support through this long process. graphic information. We will endeavor to incorporate this information into a future edition. John D. Wehr and Robert G. Sheath We are extremely grateful to the contributors of this volume who took much time and effort to research and prepare the chapters and follow through with the LITERATURE CITED reviewer’s and editorial suggestions. We extend our sincere thanks to the reviewers whose helpful com- Prescott, G.W. 1962. Algae of the Western Great Lakes Area, 2nd ments enhanced the quality of the final presentation. Edn. W.C. Brown, Dubuque, Iowa. Smith, G. M. 1950. The Freshwater Algae of the United States, 2nd The reviewers were as follows: Robert Andersen, J. Edn. McGraw-Hill, New York. Craig Bailey, Barry Biggs, Alan Brook, Alain Couté, Whitford, L.A. & Schumacher, G.J. 1984. A Manual of Fresh-Water Eileen Cox, David Czarnecki, Gary Dillard, Gary Algae, Revised Edn., Sparks Press, Raleigh, NC. 1 INTRODUCTION TO FRESHWATER ALGAE Robert G. Sheath John D. Wehr Office of Provost and Vice President for Louis Calder Center—Biological Station and Academic Affairs Department of Biological Sciences California State University, San Marcos Fordham University, San Marcos, California 92096 Armonk, New York 10504 I. Introduction G. Haptophyte Algae II. Classification H. Synurophyte Algae A. Cyanobacteria I. Diatoms B. Red Algae J. Dinoflagellates C. Green Algae K. Cryptomonads D. Euglenoids L. Brown Algae E. Eustigmathophyte, Raphidiophyte, III. Taxonomic Chapters in This Book and Tribophyte Algae A. Key F. Chrysophycean Algae Literature Cited I. INTRODUCTION (Fig.1B), having flexible cell shapes (Fig1C), with two flagella of unequal length (Fig.1D) or Algae are treated in this book in the same sense two equal flagella (Fig.1E), with cells drawn as they are in many introductory phycology texts out into hornlike extensions (Fig.1F), and (e.g., Van den Hoek et al., 1995; Sze 1998; Graham having cells contained in a hardened case or and Wilcox, 2000); that is, they are considered to be a lorica (Fig.1G). loose group of organisms that have all or most of the 2. Colonies: an aggregation of cells that are held following characteristics: aquatic, photosynthetic, together either in a loose (Fig.1H and I) or simple vegetative structures without a vascular system, tight, well organized fashion (Fig.2B, D, and E). and reproductive bodies that lack a sterile layer of pro- Depending on the algal taxon, colonies may tecting cells. As such, algae are no longer regarded as a contain a variable number of cells or they may phylogenetic concept, but still represent an ecologically be constant throughout their development meaningful and important collection of organisms. (Fig.2B). Colonies may contain flagellated or Both prokaryotic (cells that have no membrane-bound nonflagellated cells. The basis for cellular organelles) and eukaryotic taxa (cells with organelles) connection varies among colonies, including a are included. In addition, there is a wide range of surrounding gelatinous matrix (Fig.1H and I), vegetative morphologies, including the following: gelatinous stalks (Fig.2A), common parental wall (Fig. 2B), and direct attachment at the 1. Unicells: species that occur as solitary cells that cellular edges (Fig.2C) or at the middle portion may be nonmotile or motile. Motile cells may of each cell (Fig.2C). Alternately, cells may be have one or more flagella or they may glide. A connected via their loricae (Fig.2E). wide variety of forms exists among unicells, 3. Pseudofilaments: an aggregation of cells in an including those contained within a gelatinous end-to-end fashion. The cells are not directly sheath (Fig.1A), with intricate cell walls connected to each other; rather, they are spaced 1 Freshwater Algae of North America Copyright © 2003, Elsevier Science (USA). All rights of reproduction in any form reserved. 2 Robert G. Sheath and John D. Wehr FIGURE 1 Unicellular and colonial forms of freshwater algae. A. Gloeocapsa (cyanobacterium), a unicell to small grouping of cells contained within concentrically layered gelatinous sheaths (arrows). B. Micrasterias (green alga, desmid), a unicell with many regular cell wall incisions (arrows) that form a series of lobes and lobules. C. Euglena (euglenoid), a unicell that does not produce walls and can readily change shape. D. Ochromonas (chrysophycean alga), a unicell with one long and one short apically inserted flagellum (arrows). E. Pyrenomonas (cryptomonad), a unicell with two equal subapically inserted flagella. F. Ceratium (dinoflagellate), a unicell with a theca composed of cellulose plates and cellular extensions or horns (arrows). G. Strombomonas (euglenoid), a flagellated unicell within a rigid lorica (arrow). H. Coelosphaerium (cyanobacterium), a colony with spherical cells loosely arranged at the periphery of a gelatinous matrix. I. Dermatochrysis(chrysophycean alga), a colony with spherical cells in a single layer scattered in a gelatinous matrix that has distinct perforations (arrows). Scale bars = 10 μm. apart and contained in a common gelatinous (Figs.2H–J, and 3B and C). Linear colonies can matrix (Fig.2F). be distinguished from true filaments by the fact 4. Filaments: a chain or series of cells in which the that abutting colonial cells each possess their cells are arranged in an end-to-end manner, own entire walls (Fig.2D). Filaments may be where adjacent cells share a common cross wall arranged in a single series (uniseriate or 1. Introduction to Freshwater Algae 3 FIGURE 2 Colonial, pseudofilamentous, and filamentous forms of freshwater algae. A. Porphyridium (red alga), a colony with spherical cells attached together by gelatinous strands (arrows). B. Crucigenia(green alga), a colony with consistent groups of four cells produced inside the walls of the parent cells. C. Tabellaria (diatom), a colony with cells attached at their edges in a zig-zag fashion. D. Asterionella (diatom), a linear colony with cells attached only at the central region. E. Dinobryon(chrysophycean alga), a colony with cells attached by their loricae (arrows). F. Chroodactylon (red alga), a pseudofilament with cells arranged in an end- to-end pattern in a common gelatinous matrix (arrows), but not directly connected to each other. G. Zygnema (green alga), an unbranched filament without a gelatinous matrix. H. Lyngbya (cyanobacterium), an unbranched filament that is contained in a gelatinous sheath that is evident at the filament tip (arrow). I. Scytonema (cyanobacterium), a filament that produces double false branches (arrows) that result from breakage and further growth of each fragment. J. Bangia(red alga), a multiseriate filament in part with at least two cells across (arrows). Scale bars = 10μm. uniaxial) (Fig.2G–I) or they may be in more some cyanobacteria, such as Scytonema than one series of cells (multiseriate or multiaxial) (Fig.2I), by fragmentation and continued (Fig.2J). Filaments may be unbranched (Figs. growth of one or both fragments. Other types of 2G and H) or they can produce branches in a filaments include those that are heterotrichous, new plane that are morphologically similar to that is, they have a distinct prostrate system the main axis (Fig.3B) or that are quite distinct with attached erect branches. Differentiated (Fig.3C). Branching may be dichotomous or filaments have specialized cells within the chain. forked (Fig.3B), alternate (Fig.3C), opposite, or The main axis may have a surrounding layer of whorled (Fig.3D). False branches are formedin small cells termed cortication (Fig.3A). 4 Robert G. Sheath and John D. Wehr FIGURE 3 Filamentous, saclike, crustose, pseudoparenchymatous, and siphonous forms of freshwater algae. A. Compsopogon(red alga), a filamentous form with small cortical cells (arrows) covering the main filament. B. Cladophora (green alga), a filament that has dichotomous (forked) branches (arrows). C. Draparnaldia (green alga), a filament that has tuftlike lateral branches with cells that are considerably smaller than those of the main axis. D. Batrachospermum(red alga), a filament with whorllike lateral branches (arrows). E. Boldia (red alga), a saclike thallus that consists of a single layer of cells. F. Heribaudiella(brown alga), a crust that is tightly adherent to the rock substratum. G. Hildenbrandia (red alga), a cross section of a crust that shows vertical files of cells (arrows). H. Caloglossa(red alga), a pseudoparenchymatous thallus composed of a main filamentous axis (arrow) with tightly compacted lateral branches. I. Vaucheria (yellow–green alga), a sipho- nous thallus without cross walls separating the nuclei. Scale bars = 10μm, except B = 250μm, E = 1 cm, and F = 2cm. Figure A courtesy of Tara Rintoul; Figure B from Vis et al. (1994) reprinted with permission of University of Hawaii Press; Figure E from Sheath (1984) with permission; Figure G courtesy of Alison Sherwood. 5. Pseudoparenchymatous structures: tissue-like into an outer photosynthetic layer (the cortex) thalli that consist of closely appressed branches and an inner non-photosynthetic region (the of a uniseriate or multiseriate filament (Fig.3H). medulla). Most tissue-like forms in freshwater Crustose forms may be composed of short, habitats are simple, such as the saccate red alga compacted filaments, such as the brown alga Boldia,which consists of a single layer of cells Heribaudiella(Fig. 3F) and the rhodophyte (Fig.3E). Hildenbrandia(Fig.3G). 7. Coenocytic or siphonous forms: large 6. Parenchymatous forms: true tissues composed of multinucleate forms of various shapes without a solid mass of cells that is three dimensional, cross walls to separate the nuclei or other variously shaped, and not filamentous in organelles. An example is the yellow–green alga construction. The cells may be differentiated Vaucheria(Fig.3I). 1. Introduction to Freshwater Algae 5 Freshwater algae exhibit all of these morphologies, distinguished from each other based on a combination but the macroscopic pseudoparenchymatous and of characteristics, including photosynthetic pigments, parenchymatous forms tend to be smaller than those starchlike reserve products, cell covering, and other found in marine systems (Sheath and Hambrook, aspects of cellular organization (e.g., Van den Hoek 1990). In addition, planktonic (floating) forms are et al., 1995; Sze, 1998; Graham and Wilcox, 2000). typically small and microscopic, and mostly consist of There is little consensus among phycologists as to the the simpler forms. In contrast, benthic (attached) algae exact number of algal divisions; 8–11 have been recog- include the entire range of morphologies, although nized in recent texts (Van den Hoek et al., 1995; Sze, flagellated taxa are less common than in plankton. 1998; Graham and Wilcox, 2000). The 12 major algal groups (divisions and classes) recognized in this book are distinguished from each II. CLASSIFICATION other in Table I. Each of the major groupings is briefly presented in the following sections, but the reader Algae do not represent a formal taxonomic group should refer to the relevant chapter(s) for more details. of organisms, but rather constitute a loose collection of The number of freshwater genera now reported (>800) divisions or phyla with representatives that have the from North America, as discussed in Chapters 3–22, characteristics noted previously. The divisions are has greatly increased from earlier treatises (e.g., Smith, TABLE I Major Distinguishing Features of the Major Algal Groups Presented Herein Algal group Photosynthetic Chloroplast outer Thylakoid Starch-like External (chapter number) pigmentsa membranes associations reserveb coveringc Flagella Cyanobacteria chla, PE, PC, 0 0 Cyanophycean Pepitoglycan 0 (3 & 4) APC matrices or walls Red algae chla, PE, PC, 2 0 Floridean Walls with a galactose 0 (5) APC polymer matrix Green algae (6–9) chla,b 2 2–6 True Cellulosic walls, scales 0 – many Euglenoid chla,b 3 3 Paramylon Pellicle 1–2 Algae (10) emergent Yellow–green and chla,c 4 3 Chrysolaminarin Mostly cellulosic 2 unequal related algae (11) walls if present Chrysophyte chla,c 4 3 Chrysolaminarin None, scales, lorica 2 unequal algae (12) fucoxanthin Haptophyte chla,c 4 3 Chrysolaminarin Nonsiliceous scales 2 equal + algae (13) fucoxanthin haptonema Synurophyte chla,c 4 3 Chrysolaminarin Siliceous scales 2 unequal algae (14) fucoxanthin Diatoms (15–19) chla,c 4 4 Chrysolaminarin Siliceous frustule 1, reproductive fucoxanthin cells only Dinoflagellates chla,c 3 3 True Theca 2 unequal (20) peridinin Cryptomonads chla,c 4 2 True Periplast 2 equal (21) PC or PE Brown algae chla,c 4 3 Laminarin Walls with 2 unequal (22) fucoxanthin alginate matrices Source: Various phycology textbooks (e.g., Sze, 1998; and Graham and Wilcox, 2000). achl = chlorophyll (green); PE = phycoerythrin (red); PC = phycocyanin (blue); APC = allophycocyanin (blue); fucoxanthin and peridinin (golden to brown). bAll of the reserves are polymers of glucose. They differ by their linkages: cyanophycean and floridean α1, 4 and α1, 6 branches; true starch with amylose α1, 4 and amylopectin α1, 4 and α1, 6 branches; paramylon β1, 3; chrysolamin and laminarin β1, 3 and β1, 6 branches. Only true starch stains positively with iodine (purple to black). cPellicle and periplast within plasma membrane; the rest are external to it. 6 Robert G. Sheath and John D. Wehr 1950; Prescott, 1962), but is still highly tentative nonmotile colonies (Chap.7), 81 filamentous and and likely to be an underestimate of the region’s plantlike genera (Chap.8), and 48 conjugating genera biodiversity. and desmids (Chap.9). Some members of the green algae (Charophyeae) are part of a lineage that is thought to be ancestral to higher plants. A. Cyanobacteria Green algae are widespread in inland habitats, but Cyanobacteria or blue–green algae are prokaryotes, certain groups may have specific ecological require- that is, cells that have no membrane-bound organelles, ments. For example, flagellated chlorophytes tend to be including chloroplasts (Table I; Chap.3). Other charac- more abundant in standing waters that are nutrient teristics of this division include unstacked thylakoids, rich (Chap.6). Coccoid unicells and colonies are phycobiliprotein pigments, cyanophycean starch, and common in the plankton of standing waters and slowly peptidoglycan matrices or walls. There are 124 genera moving rivers when nutrients, light and temperature reported from inland habitats in North America, of are reasonably high (Chap.7). The majority of filamen- which 53 are unicellular or colonial (Chap.3) and 71 tous and plantlike Chlorophyta are attached to hard are filamentous (Chap.4). However, the taxonomy of surfaces in standing or flowing waters, but some can this division is currently in a state of flux, as noted exist in the floating state or on soils or other subaerial in Chapter 3, and the number of genera should be habitats (Chap.8). Filamentous conjugating green algae considered to be tentative. are most frequent in stagnant waters of roadside Cyanobacteria inhabit the widest variety of fresh- ditches and ponds, and in the littoral zones of lakes, water habitats on Earth and can become important where they can form free-floating mats or intermingle in surface blooms in nutrient-rich standing waters with other algae in attached or floating masses (Chap.9). (Chaps.3 and 4). Some of these blooms can be toxic to Desmids are more common in ponds and streams that zooplankton and fish, as well as livestock that drink have low conductance and moderate nutrient levels, water containing these organisms. Inland cyanobacteria and often intermingle with macrophytes. also occur in extreme environments, such as hot springs, saline lakes, and endolithic desert soils and D. Euglenoids rocks. Photosynthetic Euglenophyta or euglenoids have chloroplasts surrounded by three membranes, thyla- B. Red Algae koids in stacks of three, chlorophyll-a and -b as photo- Rhodophyta or red algae represent a division that synthetic pigments, paramylon, and a pellicle (Table I; is characterized by chloroplasts that have no external Chap.10). Ten genera are reported from North endoplasmic reticulum and unstacked thylakoids, American freshwater habitats (Chap.10). phycobiliprotein pigments, floridean starch, and lack Euglenoids are particularly abundant in the of flagella (Table I; Chap.5). They are predominantly plankton of standing waters rich in nutrients and marine in distribution; only approximately 3% of over organic matter, and they can be associated with sedi- 5000 species occur in truly freshwater habitats. In ments, fringing higher plants, and leaf litter, although North America, 25 genera are recognized in inland some may dominate in highly acidic environments habitats (Chap.5). (Chap.10). Freshwater red algae are largely restricted to streams and rivers, but also can occur in other inland E. Eustigmatophyte, Raphidiophyte, and habitats, such as lakes, hot springs, soils, caves, and Tribophyte Algae even sloth hair (Chap.5). Eustigmatophyte, raphidiophyte, and tribophyte algae comprise a loose group of algae that share the C. Green Algae following characteristics: chloroplasts with four sur- Chlorophyta or green algae constitute a division rounding membranes, thylakoids in stacks of three, that has the following set of attributes: chloroplasts chlorophyll-a and -c as the typical photosynthetic with no external endoplasmic reticulum, thylakoids pigments, and chrysolaminarin as the photosynthetic typically in stacks of two to six, chlorophyll-a and -b reserve product (where known) (Table I; Chap.11). as photosynthetic pigments, true starch, and cellulosic The yellow–green algae are quite diverse in freshwater walls or scales (Table I). This is a diverse group in habitats of North America: at least 90 genera have inland habitats of North America that includes 44 been reported, whereas the eustigmatophytes and raph- flagellated genera (Chap.6), at least 129 coccoid and diophytes are relatively small groups that comprise