Grasses of Porto Rico .''75 



leaf-sheaths very broad and reticulated, at least when dry- 

 Spikelets about 1,5 mm. long : racemes numerous. 



1. P. dcfisum. 

 Spikelets about 2.5 mm. long : racemes l2-l8. 



2. P. UnJerwoodii. 

 Third scale dark brown at maturity : basal sheaths not broad 



nor reticulated. 3. P. Boscianuin. 



Spikelets pubescent. 



Spikelets elliptic, about one half as wide as long, the pubes- 

 cence appressed. 4. P. Helleri. 

 Spikelets broadly oval or obovate, the pubescence spreading. 

 Spikelets less than 1.5 mm. long. 5. P. heviisphaerictim. 

 Spikelets 2 5-3 mm. long. 6. /'. virgatum. 

 Stems slender, creeping at the base : leaf-blades short, rarely more than 

 5 cm. long : outer scales of the spikelet without a midnerve. 



7. P. orbiciihltuin. 

 ** Spikelets surrounded by a broad toothed margin. 8. P. fiDibriatuni. 

 b. Spikelets narrowly elliptic, less than one half as broad as long : rachis of racemes 

 barely, if at all, margined. 9. P. Porloricense. 



2. Racemes long and slender, arising in pairs at the apex of the stem, rarely with another 

 one a short distance below. 10. /-*. conjugatum. 



1. P.\SR\LL'.M DENSU.M Poir. ill Lam. Encycl. 5: 32. 1804. 



A single specimen of this species from Porto Rico has been 

 seen by the writer, and is the type in the herbarium of Lamarck 

 at Paris ; it was collected by Ledru. 



2. Paspalum Underwoodii sp. nov. 



A tall perennial with reticulated basal leaf-sheaths, elongated 

 leaf-blades and rather dense inflorescence. Stems 8-12 dm. tall, 

 erect, rather stout at the base: leaves numerous at the base; 

 sheaths glabrous, the basal ones strongly reticulated, at least when 

 dry, rather abruptly narrowed into the blade at or below the mid- 

 dle, equitant ; ligule a scarious ring ; blades 4-7 dm. long, about 



1 cm. wide, long-acuminate at the summit, exceedingly rough on 

 the lower surface, densely hirsute on the upper surface, serrulate 

 on the margins: inflorescence 1.5—2.5 dm. long: racemes 12—18, 

 sessile or nearly so, ascending or nearly erect, the lower ones 7-10 

 cm. long, the rachis including its serrulate wings about i mm. 

 wide and more or less setiferous, usually purplish : spikelets in 

 pairs in two rows, on short hispid pedicels, yellowish green, usu- 

 ally more or less purplish tinged, glabrous, broadly obovate, 2.5 

 mm. long, 2 mm. broad, and about 0.8 mm. thick, apiculate, the 



2 outer scales 3-nerved, apiculate, the third scale yellowish-white, 

 oval, 2.2 mm. long and about r.7 mm. wide, minutely striate. 



Type collected by Underwood and Griggs along roadsides, 



