460 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
to the description in the revision, if the species is there described. 
No synonymy is given except such as is additional to that cited in 
the previous work. 
The distribution here given is based upon all the material at 
present in the National Herbarium, including that already cited. 
As in the earlier paper all specimens cited are in the United States 
National Herbarium, unless otherwise stated. Specimens from other 
herbaria are cited when such specimens add to the known range. 
Through the courtesy of Dr. I. Urban the grasses of the Krug and 
Urban Herbarium in the Berlin Museum were submitted for study. 
Many additional specimens are cited from this herbarium, such 
specimens being indicated by the abbreviation ‘‘K. U. Herb.’ The 
range within the region covered is graphically presented by maps. 
For the sake of comparison these maps indicate also the distribution 
in the southern border of the United States of such species as extend 
into this region. Trinidad and Tobago, though they are continental 
islands and their flora is essentially South American, are included in 
the West Indies because they are so included by Grisebach * and by 
Urban. In order to connect Panama and Trinidad the detailed 
distribution.includes Venezuela and Colombia. 
KEY TO SPECIES AND GROUPS. 
Axis of branchlets produced beyond the base of the uppermost spikelet as a point or 
bristle 1 to 6 mm. long......... cee eeeceee Subgenus PavRocHakETIvUM, p. 463. 
Axis of branchlets not produced into a bristle. (In P. geminatum and P, paludivagum 
the somewhat flattened axis pointed but not bristle-form.) 
Basal leaves usually distinctly different from those of the culm, forming a winter 
rosette; culms at first simple, the spikelets of the primary panicle not 
perfecting seed, later usually becoming much branched, the small second- 
ary panicles with cleistogamous, fruitful spikelets. 
Subgenus DicHanTHELIUM, p. 512. 
Basal leaves similar to culm leaves, not forming a winter rosette; spikelets all 
fertile. 
Plants annual. 
Spikelets plano-gibbous, the second glume swollen, bristly and burlike 
at maturity; first glume nearly as long as the minute spikelet. 
116, P. hirtum. 
Spikelets not plano-gibbous nor burlike. 
Panicles consisting of several more or less secund spikelike racemes; 
fruit transversely rugose; glumes and sterile lemma usually 
reticulate-veined................. See Fascicunara, p. 467. 
Panicles more or less diffuse (small and narrow in P. vaseyanum). 
Blades ovate-lanceolate or elliptical, one-fifth to one-fourth 
as broad as long; plants low; spikelets minute, not over 
1.5 mm. long. 
Spikelets pyriform, attenuate at base, glabrous. 
71. P. pyrularium. 
Spikelets elliptic, pubescent............. 67. P. trichoides, 
1 Fl, Brit. W. Ind. * Symb. Ant. 
