BOTANY OF THE MAYA AREA


Lemma without a contorted awn.
 Glumes membranaceous; fertile lemma indurate.
 (Panicere.)
 Spikelets subtended by bristles or enclosed in spiny
 burs.
 Spikelets subtended by bristles.
 Bristles persistent .. _-43. Setaria
 Bristles deciduous, falling with the spikelet 44. Pennisetum
 Spikelets enclosed in spiny burs ...-. 45. Cenchrus
 Spikelets neither subtended by bristles nor enclosed
 in burs.
 Spikelets arranged on one side of spikelike
 racemes.
 Margins of fertile lemma thin, not inrolled.
 Spikelets densely covered with long, tawny
 silky hairs .... 25. Trichachne
 Spikelets glabrous or pubescent but not long
 silky ...-...- ...-. 26. Digitaria
 Margins of fertile lemma inrolled, indurate.
 Rachilla joint and first glume adnate, forming
 a swollen ring-like callus.- 30. Eriochloa
 Rachilla j6int and first glume neither adnate
 nor swollen.
 Racemes solitary (see also Paspalum).
 Spikelets sunken in the thick corky rachis -27. Stenotaphrnm
 Spikelets not sunken in the rachis.
 Rachis rather broadly winged, partially
 enflding the glabrous spikelets;
 spfkelets paired, but those of a
 pair rather distant, appearing as if
 solitary in a single row ___ 28. Thrasya
 Rachis wingless; spikelets hispid, soli-
 tary, placed with the back of the
 fertile lemma turned away from
 the rachis ..____..-.29. Mesosetum
 Racemes 2 to many.
 Spikelets awned or awn pointed.
 Spikelets hispid .._ _._ _._..-41. Echinochloa
 Spikelets glabrous or pilose, not hispid-40. Oplismenus
 Spikelets awnless.
 Fertile lemma with small wings at the
 base, these sometimes reduced to
 scars 34. Ichnanthus
 Fertile lemma wingless.
 Back of the fertile lemma turned
 away from the rachis_ 31. Axonopns
 Back of the fertile lemma turned
 toward the rachis.
 First glume present 33. Panicum
 First glume usually wanting (pres-
 ent sometimes in P. langei,
 occasionally in other species)-32. Paspalum
 Spikelets paniculate. (See also Echinochloa.)
 Spikelets villous with appressed or spreading
 hairs.
 First glume obsolete; spikelets awnlesa-- 24. Leptocoryphium
 First glume minute; second glume and sterile
 lemma short awned- ._._ ._42. Tricholana
 Spikelets glabrous or pubescent.
 Fertile lemma with small wings at the base,
 these sometimes reduced to scars ..... _34. Ichnanthus