Grasses: Bromus to Paspalum, Second Edition

Illustrated Key to the GENERA of Grasses in Illinois

Illustrated Key to the GENERA of Grasses in Illinois 22. Both spikelets pedicellate, the pedicels unequal in length (Fig. 91) __________________________________50. Miscanthus 22. One spikelet sessile, the other pedicellate (or represented merely by the pedicel) . 23. Pedicellate spikelet represented only by the pedicel (Fig. 92)----------------------------53. Sorghastrum 23. Pedicellate spikelet present. 24. Both spikeIets of the pair with perfect floretL _____ _ ______________________________ 51. Erianthus 24. Only the sessile spikelet of the pair perfect. 25. Inflorescence racemose or nearly spicate. 92. Paired spikelets of Sorghastrum. 91. Paired spikelets of Miscanthus. Illustrated Key to the Genera / 41 26. Flowering culms much branched into many short leafy branchlets terminated by 1-6 racemes. 27. Racemes 2 or more from the sheaths (Fig. 93)-------------- 54· Andropogon" 27. Raceme solitary at the tip of the peduncle (Fig. 94) ------57. Schizachyrium " 26. Flowering culms unbranched___________ _ - _____________________56. Bothriochloa" 25. Inflorescence paniculate (Fig. 95) ___________ _ ____________________________52. Sorghum" 93. Inflorescence of Andropogon. 95. Inflorescence of Sorghum. 94. Inflorescence of Schizachyrium. 42 / GRASSES Group E Inflorescence solitary, racemose, or paniculate, but not spicate; each spikelet with one perfect floret (sterile or staminate lemmas may be present, in addition); no part of the spikelet awned. 1. Spikelets borne in pairs. 2. One spikelet of the pair sessile, the other pedicellate (Fig. 96) ___ - ______________________________ --55. Microstegium " 2. Both spikelets either sessile or pedicellate. 3. First glume as long as or longer than the lemmas (Fig. 97); plants 2.5-4.0 m talL __________________ 50. Miscanthus " 3. First glume absent or up to 0.5 mm long, much shorter than the lemmas; plants up to 1.5 m tall. 4. Spikelets with long, tawny hairs longer than the spikelets (Fig. 98) ____________________41. Trichachne, p. 287 4. Spikelets without long, tawny hairs exceeding the spikelets (Fig. 99) ----------------------45· Paspalum, p. 296 1. Spikelets solitary (i.e., not borne in pairs) . 5. First glume reduced to a sheath and united with the lowest, swollen joint of the rachilla (Fig. 100) ----44. Eriochloa, p. 292 96. Paired spikelets of Microstegium. 97. Spikelet of Miscanthus. 99. Paired spikelets of Paspalum. // 98. Hairy spikelet of Trichachne. Illustrated Key to the Genera / 43 5. First glume absent, reduced, or normal, neither sheath-like nor united with a swollen rachillar joint. 6. Both glumes absent (Fig. 101) ____________81. Leersia" 6. Both glumes present, although the first often much reduced or, if absent, the plants not producing seeds. 7. First glume absent (Fig. 102); plants with creeping rhizomes , rarely producing seeds________________Zoysia 1 7. First glume present, although occasionally strongly reduced ; rhizome present or absent; plants producing seeds. 8. First glume up to one-half (to % in a few species of Panicum) as long as second glume. 1 Zoysia is frequently planted in Illinois as a choice lawn grass, but no collections have ever been made of it as an adventive. Therefore, it is excluded from the text. ~oo. Spikelet of Eriochloa. -.102. Spikelet of Zoysia. 101. Spikelet of Leersia. 44/ GRASSES g. Each floret subtended by one or more bristles (Fig. 103) __________________________481. Setaria g. Florets not subtended by bristles. 10. Spikelets solitary at the end of long, capillary pedicels. 11. Fertile lemma leathery_______________ _ -----------------43. Leptoloma, p. 28g 11. Fertile lemma indurated____46. Panicum 10. Spikelets grouped in 2-4 or more ranks. 12. Inflorescence a dense, dark purple-brown panicle______________47. Echinochloa 12. Inflorescence racemose or paniculate with remote, ascending racemes. 13. Racemes 1-2 (-3) cm long________ _ ----------------47. Echinochloa 13. Racemes over 2 cm long___________ _ --------------45· Paspalum, p. 2g6 8. First glume nearly as long as the second glume, not conspicuously different in size. W3. Floret in Setaria with bristles. 14. Clumes 3-nerved (Fig. 104). 15. Spikelets 4.5-6.0 mm long; glumes 4-6 mm long; blades 2-5 mm broad______________ _ ___________________21. Hierochloe, p. 186 15. Spikelets 2.0-3.5 mm long; glumes 2-3 mm long; some or all the blades over 5 mm broad. 16. Lemmas 5-nerved; spikelet with one perfect and one sterile lemma (Fig. 105); blades to 8 mm broad_______________ _ _______________26. Beckmannia, p. Ig8 104. Glume of Hierochloe. 105. Spikelet of Beckmannia. Illustrated Key to the Genera / 45 16. Lemma nerveless; spikelet with one perfect lemma (Fig. 106); blades to 20 mm broad______________25. Milium, p. 197 14. Glumes I-nerved. 17. Lemma with a conspicuous tuft of hairs at the base (on the callus) (Fig. 107 h spikelets 6-7...