188 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
Fruits indurated-rigid (or if thin not open at the summit nor 
hyaline-margined). 
Spikelets placed with the back of the fruit turned away 
from the main axis. . 
First glume and rachilla joint forming a swollen ring- 
like callus; fruit mucronate or shortly awn-pointed. 
22. Eriochloa (p. 207). 
First glume present or wanting, not forming a ring-like 
callus; spikelets in slender racemes. 
First glume as long as the spikelet or nearly so; 
spikelets swollen on the side toward the axis and 
fitting into alternate hollows; inflorescence a sin- 
gle raceme .............. 27. Mesosetum (p. 211). 
First glume wanting or not over one-fourth the 
length of the spikelet. 
Racemes racemose along the main axis; first 
glume present....... 28. Brachiaria (p. 212). 
Racemes digitate or subdigitate, first glume 
wanting............ 20. Axonopus (p. 207). 
Spikelets with the back of the fruit turned toward the main 
axis. 
Spikelets plano-convex, subsessile in spike-like 
racemes, typically lacking the first glume (both 
glumes wanting in P. pulchellum). 
19. Paspalum (p. 199). 
Spikelets unequally biconvex; paniculate, or if race- 
mose the first glume present. 
Fertile florets 2.............. 23. Isachne (p. 208). 
Fertile floret 1. 
Glumes awnless. 
Second glume broad and saccate, panicle 
contracted or spike-like. 
30. Sacciolepis (p. 212). 
Second glume not broad nor saccate. 
Margins of lemma inrolled; no lateral 
appendages nor excavations at base 
of fruit.....32. Panicum (p. 214). 
Margins of lemma not inrolled; either 
lateral appendages or excavations 
at base of fruit. 
33. Ichnanthus (p. 228), 
Glumes or one of them awned, or cuspidate. 
Fruit cuspidate, palea free at the tip; 
second glume and sterile lemma tapering 
into an awn or cuspidate point. 
31. Lehinochloa (p. 213). 
Fruit not cuspidate, palea not free; awns 
arising from a toothed summit. 
Spikelets clothed with rose-colored 
silky hairs; first glume minute. 
34. Tricholaena (p. 229). 
Spikelets pubescent with short pale 
hairs, first glume nearly as long as 
the second.35. Oplismenus (p. 229). 
