A Preliminary Enumeration of the Grasses of Porto Rico 



I5y Gkorgk V. Nash 



This enumeration is based mainly upon the material in the 

 herbarium of the New York Botanical Garden. The collections of 

 Heller, Underwood and Griggs, Wilson and Goll are there fully 

 represented, and those of Sintenis partially so. A few species, of 

 which we have not seen specimens, have been admitted upon the 

 authority of monographers. Further explorations of the island 

 must add more species, and it is hoped that this enumeration may 

 serve as a help in such further exploration. That this work may 

 be facilitated, it has been deemed advisable to incorporate analyt- 

 ical keys to the tribes, genera and species. This enumeration 

 credits the island with lO of the 13 grass tribes, 37 genera, and 

 75 species and varieties, among them 9 hitherto unknown. 



Key to tlie Tribes 



A. Spikelets falling from the pedicel entire, naked or enclosed in bristles or a hur-like 

 involucre, or immersed in the internodes of a readily disarticulating racliis, i- 

 flowered, or if a-flowered the lower flower staminate (perfect in Isachne) : in- 

 ternodes of the rachilla of the spikelet very short, not measurable. 

 Spikelets round or somewhat dorsally compressed : hilum punctiform. 



Flowering scale and palet hyaline, thin, much more delicate in structure than 

 the thick-membranous to coriaceous empty scales. 

 Spikelets unisexual. Tribe I. Maydeae. 



Spikelets in pairs, one sessile, the other pedicellate, the former perfect, 

 the latter sometimes perfect, often with a staminate flower, or fre- 

 quently empty, abortive or wanting. Tribe II. Andkoi-oooneae. 

 Flowering scale, at least that of tlie perfect flower, similar in te.xture to the 

 empty scales, or frecpiently thicker and tirmer, never liyaline and thiji. 

 [The preceding number of the Bulleti.n, Vol. 30, Nq. 6, for June, 1903 (30: 

 319-368), was issued II Je 1903.] 



3GiJ 



