AGROSTIDE^. 283 



"between them. Stamens 2-3. Styles very short. Grain free, 

 readily falling away from the glume, the pericarp loosely enclos- 

 ing the seed or very thin and evanescent. 



Perennials or rarely appearing to be annuals, often slender, the 

 leaf -blades flat or convolute-terete. 



There are about 80 species Avidely spread over the trojiical, 

 subtropical, and temperate regions of both the New and the Old 

 World, mostly, however, American. 



Sporobolus was included by the older authors in Agrostis. R. 

 Brown first pointed out the differences in the fruit and took as the 

 principal character the loose membranous pericarp readily detach- 

 able from the seed, but this is not apparent in the dried state in all 

 species. When soaked in water the pericarp is easily removed. As 

 a whole, Sjmi'oholus is chiefly distinguished from Agrostis by the 

 total absence of any dorsal awn, and by the grain so loosely enclosed 

 in the glume that it usually protrudes from it when ripe, and 

 often falls away. See Vol. 1, p. 43. The palea also generally splits 

 readily iiito two, a diameter which Grisebuch took for a new genus, 

 Diacliyrium, and which Nees figured and described as a two-valved 

 pericarp, a character unknown in Gramineffi, Two species, S. 

 compi'essus and S. serotinus, occasionally have two flowers to a 

 spikelet. 



A. Plant slender, only 2-4 cm. high, spikelets 1 mm, long. 1 



B, Plants taller and stouter (b) 



b. Floral glume 5-6 mm, long (c) 



c. Panicle terminal 2 



c. Panicles terminal and lateral 3 



b. Floral glume 3-4.5 mm. long (d) 



d. Empty glumes subequal (e) 



e. Floral glume 4-4.5 mm. long 4 



e. Floral glume 3-3.5 mm. long 6, 6 



d. Empty glumes unequal (f) 



f. Floral glume 3.5 mm., first glume 1.6 mm., 

 second glume 2.5 mm. long 7 



f. Floral glume 3-4 mm., first glume 2-3 mm., 

 second glume 3.5-5.5 mm. long 8 



