460 CONTRIBUTIOlSrS FROM THE NATIONAL HEEBARIUM. 



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 GEOUPS. 



Axis of branchlets produced beyond the base of tbe uppermost spikelet as a point or 



bristle 1 to 6 mm. long Subgenus PAURocHAETirM, 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 Dichakthelium, p. 512. 

 Basal leaves similar to ciilm leaves, not forming a winter rosette; spikelets all 

 fertile. 

 Plants annual. 



Spikelets piano-gibbous, the second glume swollen, bristly and burlike 

 at maturity; first glume nearly as long as the minute spikelet. 



116. P. hirtum. 

 Spikelets not piano-gibbous nor burlike. 



Panicles consisting of several more or less secund spikelike racemes; 

 fruit transversely rugose; glumes and sterile lemma usually 



reticulate- veined See Fasciculata, p. 467. 



Panicles more or less diffuse (small and narrow in P. vaseyamim). 

 Blades ovate-lanceolate or elliptical, one-fifth to one-fourth 

 / as broad aa long; plants low; spikelets minute, not over 



1.5 mm. long. 

 Spikelets pyriform, attenuate at base, glabrous. 



il. P. pyrularium. 

 Spikelets elliptic, pubescent 67. P. trichovles^ 



' Fl. Brit. W. Ind. - Symb. Ant. 



