Part 2, 1912] POACEAE 
Spikelets glabrous. 
Spikelets nearly orbicular, all with 4 scales, 
Spikelets elliptic or obovate, of 3 scales, or the lower of each 
pair often with an additional scale at the base. 
Spikelets 1.5-2 mm. long, of 3 scales. 29. P. Lloydtt. 
Spikelets more than 2 mm. long, the lower of each pair often 
with an additional scale at the base. 30. P. culiacanum. 
Spikelets pubescent. 
Spikelets of 3 scales, or the lower of each pair sometimes with an 
additional basal scale. 31. P. macrophyllum. 
Spikelets of 4 scales, or rarely the second spikelet of each pair 
of 3 scales only. 
Spikelets less than 2,5 mm. long, the first scale of the lower 
28. 
P. guatemalense. 
spikelet usually short and rounded. 32, P. Langet. 
Spikelets 2.5 mm. long or more, the first scale of the lower 
spikelet usually one half its length or more and long- 
acuminate. 
Spikelets 2.5-2.8 mm. long. 
Spikelets 3~-3.2 mm. long. 
33 
34, 
VI. PULCHELLA. 
One species. 35. 
VIL. FILIFORMIA. 
Fruiting scale much shorter than the empty scales, about two thirds 
as long. 36. P. allernifiorum, 
Fruiting scale as long as the empty scales or nearly so. 
Spikelets transversely rugose. 
Spikelets not rugose. 
Leaf-blades slender, less than 1mm. wide, involute. 
Spikelets less than 2 mm. long, glabrous. 
Spikelets elliptic, more than one half as broad as long; 
leaf-blades straight, setaceous. 
Spikelets elliptic-oblong, less than one half as broad as 
long; leaf-blades capillary, curved. 
Spikelets more than 2 mm. long, pubescent. 
Leaf-blades broad, flat, more than 1 mm. wide. 
Spikelets glabrous. 
Spikelets elliptic, about one half as broad aslong ; racemes 
2 cm. long or more. 
Spikelets broadly oval, two thirds as broad as long or more; 
37. 
iss) 
39. 
40. 
. PB. cilitferum, 
. PB. vartabile, 
. BP. pulchellum. 
P. filiforme. 
38. P, lepiocaulon. 
P. capillifolium, 
P. rotiboellioides. 
41. P. Leoninum, 
racemes less than 1.5 cm. long. 42. P. breve. 
Spikelets pubescent. 43. P. rupestre. 
VIII. PARVIFLORA. 
One species. 44. P. parvifiorum, 
IX. LAEVIA. 
Spikelets manifestly plano-convex. 
Spikelets transversely rugose. 45. P. nanum. 
Spikelets not rugose. 
Spikelets one half as thick as broad or more, the empty scales firm. 
Leaf-sheaths glabrous, or merely ciliate. . P. laeve, 
Leaf-sheaths hirsute with long weak hairs. 
Blades glabrous on the lower surface, short. 47, P. longipilum, 
Blades hirsute on both surfaces. 
Spikelets one fourth to one third as thick as broad, the empty 
scales very thin and wrinkled. ; 
Spikelets flat on both sides, or slightly convex on one side. 
Spikelets orbicular to broadly obovate. 
Leaves, excepting sometimes the exterior basal sheaths, glab- 
rous. 
Spikelets 2-2.5 mm. long. 
Spikelets 2.75-3.5 mm. long. 
Leaves, sheaths and blades or either, hirsute. 
Sheaths densely hirsute. 
Sheaths glabrous, or merely the basal ones hirsute. 
Spikelets elliptic, acutish. 
Spikelets glabrous. 
Spikelets pubescent. 
X. TENELLA. 
Spikelets 2 mm. long ; leaf-blades hirsute. 
Spikelets 2.5-3mm. long ; leaf-blades glabrous, at least on the surfaces. 
Spikelets pubescent. 57. 
Spikelets glabrous. 
XI. PORTORICENSIA. 
One species. 
XII. MAcuLata. 
One species. 
59. 
60. 
. BP. plenipilum, 
49. P. circulare. 
. BP. praecox, 
. BP. glaberrimum, 
. P. Curtisianum. 
. PB. tardum. 
. PB. lividum. 
. P. Buckleyanum, 
. PB. lenellum, 
P. pubifiorum, 
. P. geminum, 
P. portoricense. 
P. maculatum, 
169 
