Nuytsia The journal of the Western Australian Herbarium 29:217-227 Published online 13 December 2018 SHORT COMMUNICATION A key to Ptilotus (Amaranthaceae) in Western Australia Ptilotus R.Br. (Amaranthaceae) is a genus of approximately 120 species, all of which are native to continental Australia and with most of the diversity occurring in Western Australia (Hammer et al. 2015). The key presented here for 96 Western Australian taxa is a continuation of on-going work to produce an Australia-wide key for Ptilotus by the authors, which was originally presented on KeyBase (available at http://keybase.rbg.vic.gov.au/keys/show/6609, accessed 16 August 2018; previously mentioned in Hammer & Davis 2018). The Western Australian key was constructed by examining specimens lodged at the Western Australian Herbarium (PERTH) and includes all of the 93 named species now recognised (i.e. excluding P petiolatus Farmar and including P. unguiculatus T.Hammer; see Hammer 2018). The subspecies of P. polakii F.Muell., P. sericostachyus (Nees) F.Muell. and P. stirlingii (Findl.) F.Muell. are also included in the key. However, the infraspecific taxa of P. drummondii (Moq.) F.Muell., P. obovatus (Gaudich.) F.Muell. and P. schwartzii (F.Muell.) Tate, currently recognised on the plant census for Western Australia, were excluded pending on-going studies into their taxonomic status. Also excluded from the key are the phrase names P. sp. Beaufort River (G.J. Keighery 16554), P. sp. MtNarryer (A.S. George 17484) andP. sp. Porongorup (R. Davis 10805), which are in need of further study. As new species are discovered (e.g. Davis & Hammer 2018; Hammer & Davis 2018) and new evidence is found to change existing taxonomic concepts (e.g. Hammer et al. 2018a, 2018b), there will no doubt be future revisions needed to this Western Australian key. An interactive version of it is available on KeyBase (http://keybase.rbg.vic.gov.au/keys/show/6627, accessed 8 August 2018) as part of the Flowering plants of Western Australia project. Notes on distinctive characters We use ‘sepal’ in this key instead of the traditionally used ‘tepaT to describe the uniseriate perianth of Ptilotus (for more information, see Hammer 2018). All species of Ptilotus have five sepals, with two outer enclosing three inner in bud. Inner and outer sepals may differ conspicuously in morphology, or may be almost indistinguishable in fully open flowers. The term ‘clawed’ refers to the base of the sepal being conspicuously narrower than the dilated apex. Enclosing the base of the solitary flower are two opposite bracteoles (i.e. the prophylls), which in Ptilotus are membranous and can be translucent or opaque and hairy or glabrous. At the base of the bracteoles is a single bract, which is alternate to the two bracteoles (for more information on this flowering arrangement, see Acosta et al. 2009). The morphology of the bract and the bracteoles is often diagnostic. Early steps in the key include the placement of the style on the ovary summit, and the number of fertile stamens. The style is usually either clearly central or clearly excentric (see Figure 4 in Hammer et al. 2015); where this is ambiguous or where we have found infraspecific variation, we have included the species in both sections of the key. The androecium ofPtilotus is 5-merous, usually comprising a distinct androecial cup with stamens or staminodes opposite the sepals (Figure 1 A, B). Commonly, one or more stamens are infertile and reduced to staminodes. The number of fertile stamens is consistent within species and across geographic ranges (e.g. Hammer et al. 2018b), with the exception of P. manglesii © Department of Biodiversity, Conservation and Attractions 2018 ISSN 2200-2790 (Online) https://florabase.dpaw.wa.gov.au/nuytsia/ ISSN 0085-4417 (Print) 218 Nuytsia Vol. 29 (2018) Figure 1. Morphology of the androecium in Ptilotus. A - five fertile stamens opposite sepals in P. luteolus (Beni & H.Eichler) R.W.Davis; B - five fertile stamens opposite sepals in P. grandiflorus F.Muell.; C - reduced stamen number to two with three showy staminodes in P. appendiculatus Beni; D - reduced stamen number to four with an inconspicuous staminode in P. gaiidichaudii (Steud.) J.M.Black. Horizontal arrows indicate staminodes (C, D) and vertical arrows indicate fertile stamens (C). Photographs by R. Davis (A) and T. Hammer (B-D). (Lindl.) F.Muell., which may have three to five fertile stamens in different flowers on an individual plant. Infertile stamens (staminodes) may be showy (sometimes flattened and coloured; Figure 1C) or may comprise a reduced filament that appears as an inconspicuous appendage on the staminal cup (Figure ID). In some species a staminode may be so reduced that it appears as just a minute projection on the staminal cup or, rarely, may appear completely absent. In addition, some species have small appendages (previously called ‘pseudostaminodes’) that project from the staminal cup and alternate with the stamens or staminodes. Many species of Ptilotus are gynodioecious, i.e. populations comprise a mix of male-sterile (i.e. functionally female) and bisexual plants (Stewart & Barlow 1972; Hammer et al. 2018a; Figure 2). Bisexual plants have a fully developed androecium comprising one to five fertile stamens and up to four staminodes as described above. In male-sterile plants, all of the fertile stamens fail to fully form, leaving reduced appendages with clearly non-functional anthers (Figure 2B). While gynodioecy is common in the genus, it has not been adequately surveyed between and within species. In some species T. A. Hammer et al, A key to Ptilotus (Amaranthaceae) in Western Australia 219 Figure 2. Variation of stamens in the gynodioecious P. obovatus, showing flowers of a bisexual individual on the left and a female individual on the right. Arrows indicate fertile (A) and poorly-developed (B) anthers. Photographs by R. Davis (A) and K. Thiele (B). (e.g. P. obovatus and P. schwartzii) the ratio of male-sterile to bisexual plants may be very high; in others, occasional male-sterile individuals may be found in populations that are mostly bisexual (e.g. P. exaltatus Nees; Hammer et al. 2018a). Male-sterile individuals can be identified using this key, but care should be taken in couplet 3 to discriminate stamens (with poorly developed anthers) from staminodes (which lack anthers). Stamens with anthers in such individuals are counted as fertile in this couplet, despite being functionally sterile. One species (P. crispus Beni) is truly dioecious, with all individuals either female and lacking an androecium, or male with the ovary reduced and lacking a style. Indumentum in all species comprises multi-cellular hairs, ranging from simple to branching, i.e. verticillate or dendritic (see Hammer et al. 2015, 2017 for discussions and figures). Simple hairs are described as nodose when the nodes between hairs are swollen and septate when they are not. Verticillate hairs have distinct whorls of side-branches at the nodes; in dendritic hairs, the side-branches do not form distinct whorls. Key to Ptilotus in Western Australia Taxa marked with an asterisk appear more than once in the key. 1. Sepals < 1.6 mm long; flowers unisexual, the males lacking styles, the females lacking sterile stamens.P. crispus 1: Sepals 2-50 mm long; flowers bisexual, or functionally female with sterile stamens 2. Style excentrically placed on the ovary summit 3. Fertile stamens 1 or 2 4. Ovary glabrous 5. Stems herbaceous 6. Fertile stamen 1.P. alexandri 6: Fertile stamens 2 220 Nuytsia Vol. 29 (2018) 7. Adaxial surface of inner sepals with a basal tuft of hairs 8. Leaves thick, semi-succulent to succulent; flowers green; sepals with short, appressed hairs on abaxial surface.P. chortophytus 8: Leaves flat, not semi-succulent or succulent; flowers pink to purple; sepals with long, spreading hairs on abaxial surface 9. Plants decumbent; bracts 1.8-4.5 mm long; bracteoles 3-5 mm long.P. stirlingii subsp. stirlingii 9: Plants prostrate; bracts 5.3-6 mm long; bracteoles 5.4-6.3 mm long.P. stirlingii subsp. australis 7: Adaxial surface of inner sepals ± glabrous 10. Staminodes conspicuous, c. 2 mm long.P. halophilus 10: Staminodes minute or absent 11. Bracts 6.5-7 mm long.P. sericostachyus subsp. roseus 11: Bracts 4-5.7 mm long.P. sericostachyus subsp. sericostachyus 5: Stems woody or basally woody 12. Leaves petiolate 13. Glabrous portion of outer sepal apex 3-5 mm long; bracts ± equal in length to bracteoles; style 6-10 mm long.P. polakii subsp. polakii 13: Glabrous portion of outer sepal apex 1-2 mm long; bracts shorter than bracteoles; style 4-5.5 mm long.P. polakii subsp. juxtus 12. Leaves sessile or subsessile 14. Stems erect or ascending; leaves not crowded at the base of the stem.P. bcardii 14: Stems prostrate, mat-forming; leaves crowded at the base of the stem 15. Sepals < 7 mm long, apex not rounded (presumed extinct).P. caespitulosus 15: Sepals > 8 mm long, apex rounded.P. fasciculatus 4: Ovary hairy 16. Stems herbaceous 17. Inner sepals with a prominent basal tuft of hairs inside 18. Leaves with persistent verticillate hairs on adaxial surface to 2 mm long.P. andersonii 18: Leaves glabrous or glabrescent 19. Flowers pink; sepal apex rounded and dilated; lower portion of sepals densely hairy.P. chippcndalci 19: Flowers creamish green; sepal apex acute, not dilated; lower portion of sepals glabrous.P. seminudus 17: Inner sepals without basal tuft of hairs inside 20. Bracts longer than bracteoles.P. blackii 20: Bracts shorter than bracteoles T. A. Hammer et al, A key to Ptilotus (Amaranthaceae) in Western Australia 221 21. Leaves with persistent villous indumentum.P. appendiculatus 21: Leaves mostly glabrous.P. axillaris 16: Stems woody or basally woody 22. Bracts shorter than bracteoles 23. Stems divaricately branching.P. lazaridis 23: Stems with no pattern of branching, i.e. not divaricate 24. Leaves > 3 mm wide, not in fascicles 25. Leaves with persistent verticillate hairs.P. kenneallyanus* 25: Leaves glabrous.P. stipitatus 24: Leaves < 1.6 mm wide, in fascicles 26. Stems hairy; sepals 15-19 mm long.P. daphne 26: Stems glabrous; sepals 11-13 mm long.P. rigidus 22: Bracts longer than bracteoles 27. Leaves glabrous or glabrescent, incurved, semi-succulent.P. yapukaratja 27: Leaves with persistent verticillate hairs, not as above.P. kenneallyanus* 3: Fertile stamens 3-5 28. Ovary glabrous 29. Stems prostrate or decumbent 30. Annuals 31. Outer sepals at least 10 mm longer than inner sepals.P. crosslandii 31: Outer and inner sepals similar in size 32. Sepals glabrous, apex truncate-serrate.P. grandiflorus* 32: Sepals with straight hairs on abaxial surface, apex acute.P. procumbens 30: Perennials 33. One stamen modified into a conspicuous staminode to 17 mm long.P. declinatus 33: Stamens all fertile or staminodes short and inconspicuous 34. Sepals with hairs exceeding the apex.P. symonii 34: Sepals with hairs not exceeding the apex 35. Inflorescences becoming long-cylindrical; basal leaves distinctly spathulate.P. spathulatus 35: Inflorescences mostly ovoid; basal leaves oblanceolate 36. Plants single-stemmed.P. clivicola 36: Plants multi-stemmed 37. Sepals white to green; bracts prominently sickle-shaped.P. falcatus 37: Sepals pink; bracts not sickle-shaped.P. manglesii* 29: Stems erect 38. Leaves with hairs obscuring surface 222 Nuytsia Vol. 29 (2018) 39. Staminodes absent or obscure.P. eriotrichus 39: Staminodes prominent and coloured 40. Staminodes pink; sepals 12-20 mm long.P. sessilifolius 40: Staminodes yellow; sepals 6.5-9.5 mm long.P. incanus 38: Leaves glabrous or with sparse hairs not obscuring the surface 41. Stems woody or basally woody, divaricately branching.P. divaricatus 41: Stems herbaceous, not divaricately branching 42. Small herb < 8 cm tall; basal rosette of spathulate leaves.P. pyramidatus 42: Herbs > 8 cm tall; leaves not as above 43. Sepals with hairs restricted to midrib of abaxial surface.P. gaudichaudii* 43: Sepals with hairs not restricted to midrib of abaxial surface 44. Bracts opaque; fertile stamens 3 45. Flowers purple to pink; sepals gaping widely at anthesis, straight; ovary obscured by a plug of woolly hairs at the base of the sepals.P. exaltatus* 45: Flowers creamish green, rarely with a pale pink flush; sepals not gaping widely at anthesis, ± falcately down-curved; ovary not obscured, the hairs at the base of the sepals ± erect, not forming a woolly plug.P. nobilis* 44: Bracts translucent; fertile stamens 4 or 5 46. Sepal abaxial surface glabrous apart from basal hairs; flowers pink; fertile stamens 5.P. grandiflorus* 46: Sepal abaxial surface hairy apart from apex; flowers cream to green; fertile stamens 4 47. Inflorescences 30-60 mm wide; flowers not opening broadly, radially symmetric; old flowers not appressed to rachis.P. macrocephalus* 47: Inflorescences 18-28 mm wide; flowers opening broadly, bilaterally symmetric; old flowers appressed to rachis.P. polystachyus* 28: Ovary hairy 48. Perennials 49. Inflorescences interrupted.P. distans 49: Inflorescences not interrupted 50. Stems prostrate or decumbent 51. Bracts dark, opaque; sepal apex glabrous for 4-8 mm, truncate-serrate.P. manglesii* 51: Bracts translucent; sepal apex hairy, acute.P. holosericeus 50: Stems erect 52. Stems woody or basally woody (when young); sepals without densely woolly indumentum on the adaxial surface; staminodes 2, flattened, yellow and showy.P. obovatus 52: Stems herbaceous; sepals with densely woolly indumentum on the adaxial surface; staminodes 2, filiform, not showy, obscured by woolly sepal hairs.P. exaltatus* T. A. Hammer et al, A key to Ptilotus (Amaranthaceae) in Western Australia 223 48: Annuals 53. Inner sepals adaxially glabrous 54. Outer sepals much longer than inner.P. trichocephalus 54: Outer and inner sepals subequal 55. Sepals with hairs restricted to midrib on abaxial surface 56. Sepals 10-15 mm long; anthers > 0.9 mm long.P. gaudichaudii* 56: Sepals 6-9 mm long; anthers < 0.6 mm long.P. eremita 55: Sepals with hairs not restricted to midrib on abaxial surface 57. Sepal apex truncate-serrate; flowers orange to yellow.P. carlsonii 57: Sepal apex acute; flowers creamish green, sometimes with pale pinkish tinge 58. Stems prostrate, sprawling; sepals < 6 mm long.P. aervoides* 58: Stems erect or ascending; sepals > 8 mm long 59. Ovary with a distinct coma of hairs.P. fusiformis 59: Ovary without a distinct coma of hairs 60. Inflorescences 30-60 mm wide; flowers not opening broadly, radially symmetric; old flowers not appressed to rachis.P. macrocephalus* 60: Inflorescences 18-28 mm wide; flowers opening broadly, bilaterally symmetric; old flowers appressed to rachis 61. Pedicel (i.e. the stalk attaching the bract and flowering unit to the rachis) after abscission squat, with a prominent disc at apex; ovary gibbous; staminal cup with sparse, short hairs.P. polystachyus* 61: Pedicel (i.e. the stalk attaching the bract and flowering unit to the rachis) after abscission slender, with a reduced disc at apex; ovary not gibbous; staminal cup with copious, long, silky hairs.P. giganteus 53: Inner sepals adaxially hairy or with row of hairs on inwardly folding margins 62. Inflorescences interrupted.P. tetrandrus 62: Inflorescences not interrupted 63. Bracts glabrous, translucent 64. Flowers green; sepals >15 mm long; staminode inconspicuous.P. macrocephalus* 64: Flowers pink; sepals <10 mm long; staminode conspicuous 65. Sepals > 6 mm long; staminode > 3 mm long; anthers > 0.6 mm long.P. helipteroides* 65: Sepals < 5.5 mm long; staminode < 2.6 mm long; anthers < 0.6 mm long.P. actinocladus 63: Bracts hairy, opaque 66. Sepals <10 mm long.P. carinatus 66: Sepals >16 mm long 67. Flowers purple to pink; sepals gaping widely at anthesis, straight; ovary obscured by a plug of woolly hairs at the base of the sepals.P. exaltatus* 224 Nuytsia Vol. 29 (2018) 67: Flowers creamish green, rarely with pale pink flush; sepals not gaping widely at anthesis, ± falcately down-curved; ovary not obscured, the hairs at the base of the sepals ± erect, not forming a woolly plug.P. nobilis* 2: Style centrally placed on the ovary summit 68. Leaves persistently hairy 69. Stems herbaceous 70. Bracts and bracteoles longer than sepals.P. decipiens* 70: Bracts and bracteoles shorter than sepals 71. Inflorescences nodding; flowers creamish green 72. Bracteoles glabrous; leaves to 45 mm long with velvety indumentum.P. gardneri 72: Bracteoles pilose; leaves to 90 mm long with villous indumentum.P. clementii 71: Inflorescences not nodding; flowers pink.P. helipteroides* 69: Stems woody or basally woody 73. Ovary glabrous 74. Abaxial sepal hairs woolly, clearly exceeding apex.P. albidus 74: Abaxial sepal hairs not woolly, not exceeding apex 75. Leaves > 30 mm wide 76. Sepals and staminal filaments pink; inflorescences > 30 mm wide.P. rotundifolius 76: Sepals creamish green; staminal filaments white; inflorescences <21 mm wide.P. marduguru 75: Leaves < 20 mm wide 77. Leaves narrowly oblanceolate to narrowly elliptical.P. wilsonii 77: Leaves ovate to spathulate 78. Stems and leaves with yellow, villous indumentum of long, branching hairs.P. luteolus 78: Stems and leaves with grey-green, tomentose indumentum of short, branching hairs.P. astrolasius 73: Ovary hairy 79. Stamens longer than sepals.P. helichrysoides 79: Stamens shorter than sepals 80. Flowers interrupted, in solitary, terminal spikes.P. royceanus 80: Flowers densely arranged, in terminal panicles.P. mollis 68: Leaves glabrous or glabrescent, or mature plants leafless 81. Stems erect 82. Staminal cup appendages present 83. Bracteoles longer than sepals.P. latifolius 83: Bracteoles shorter than sepals 84. Sepals green; inflorescences > 24 mm wide. P. benlii 84: Sepals pink to pale pink or whitish; inflorescences < 20 mm wide T. A. Hammer et al, A key to Ptilotus (Amaranthaceae) in Western Australia 225 85. Stems leafless at maturity.P. aphyllus 85: Stems with leaves at maturity 86. Erect, slender herbs; taproot fleshy; inflorescences cylindrical. P. calostachyus 86: Rounded herbs or subshrubs (stems basally woody); taproot woody; inflorescences globular to ovoid 87. Stems becoming woody, branching; leaves narrow-linear, sparse.P. schwartzii 87: Stems herbaceous, simple; leaves lanceolate to spathulate, basally crowded.P. drummondii* 82: Staminal cup appendages absent 88. Inner sepals glabrous on adaxial surface 89. Stems herbaceous 90. Sepal abaxial surface glabrescent, hairs concentrated at apex.P. decalvatus 90: Sepal abaxial surface with persistent hairs at base or throughout 91. Sepals woolly at base of abaxial surface, glabrous at apex.P. gomphrenoides* 91: Sepals villous throughout length of abaxial surface.P. lanatus 89: Stems woody 92. Style ± straight.P. arthrolasius 92: Style conspicuously sigmoid.P. chrysocomus 88: Inner sepals with hairs on adaxial surface or on inner margins 93. Inner sepals clawed 94. Inflorescence units in corymb- or umbel-like clusters. 95. Inflorescence units hemispherical to ovoid, in loose corymbs.P. corymbosus 95: Inflorescence units obovoid, in dense umbel-like clusters.P. johnstonianus 94: Flowers not clustered as above 96. Staminal filaments narrowly ligulate, dilated into a disc under anthers.P. conicus 96: Staminal filaments not as above 97. Bracts and bracteoles with an awn-like apex 98. Staminal cup with divergent, forked appendages.P. capitatus 98: Staminal cup without appendages.P. spicatus 97: Bracts and bracteoles without awn-like apex.P. mitchellii* 93: Inner sepals not clawed 99. Abaxial sepal hairs exceeding sepal apex 100. Bracteoles as long as sepals.P. villosiflorus 100: Bracteoles at most half the length of sepals.P. subspinescens 99: Abaxial sepal hairs not exceeding sepal apex 101. Inflorescences nodding; staminal cup long and tube-like, 8-11 mm long. . . . P. auriculifolius 101: Inflorescences not nodding; staminal cup short, < 1.5 mm long 226 Nuytsia Vol. 29 (2018) 102. Bract apex aristate.P. decipiens* 102: Bract apex not aristate.P. mitchellii* 81: Stems prostrate or decumbent 103. Inner sepals hairy adaxially 104. Sepal apex acute 105. Plants mat-forming; stems prostrate, persistently stellate-hairy.P. roei 105: Plants not mat-forming; stems decumbent or erect, glabrous or glabrescent 106. Staminal cup appendages present.P. drummondii* 106: Staminal cup appendages absent 107. Sepals conspicuously clawed.P. unguiculatus* 107: Sepals not clawed.P. esquamatus 104: Sepal apex truncate-serrate 108. Sepals 3.5-4.5 mm long, sparsely silky-hairy abaxially.P. exiliflorus 108: Sepals 5-7.7 mm long, densely woolly abaxially.P. humilis 103: Inner sepals glabrous adaxially 109. Ovary villous-woolly at summit.P. aervoides* 109: Ovary glabrous 110. Sepals not clawed 111. Inflorescences ± pedunculate; outer sepals with a rounded apex; inner sepal midrib region 0.5-0.8 mm wide.P. gomphrenoides* 111: Inflorescences sessile; outer sepals acute; inner sepal midrib region 0.2-0.3 mm wide.P. murrayi 110: Sepals conspicuously clawed 112. Staminal cup appendages present.P. chamaecladus 112: Staminal cup appendages absent.P. unguiculatus* Acknowledgements The authors acknowledge the Curator and staff of the Western Australian Herbarium (PERTH) for their helpful assistance. We thank users of the earlier versions of the key on KeyBase who provided helpful feedback, especially Steven Dillon and Michael Hislop. We also thank Terena Lally for discussions on the dioecy of Ptilotus crispus. T. Hammer acknowledges the support of a Forrest Research Foundation PhD scholarship and University Postgraduate Award (UWA). References Acosta, J.M., Perreta, M., Amsler, A. & Vegetti, A.C. (2009). The flowering unit in the synflorescences of Amaranthaceae. The Botanical Review 75: 365-376. Davis, R.W. & Hammer, T.A. (2018). Ptilotus yapukaratja (Amaranthaceae), a new species from the Gascoyne bioregion of Western Australia. Nuytsia 29: 157-160. Hammer, T.A. (2018). The Ptilotus murrayi species group: synonymisation of P. petiolatus under P. murrayi and description of the new Western Australian species P. unguiculatus (Amaranthaceae). Swainsona 31: 93-100.