122 Botanisches Centralblatt. — Beiheft 2. 



In habit Vilfa scarcely diflfers from Sporoboliis ; S. Virginicus- 

 and S. jpungens, botli Vilfae with Beauvais, are certainly verj 

 characteristic species by their stoloniferous habit, but they are 

 just as unlike most of the other species of Vilfa as those of 

 SporohohiSj S. vaginaeflorus and aS. cuspidatus, both Vilfae, 

 represent a mode of growth which is also to be observed in 

 several species of Sporobolus proper for instance Ä depauperatus 

 and brevicalyx, while S. argutus (Vilfa) has the habit of S. junceus 

 and tenacissimus with a single, terminal panicle. Anatomically 

 these species of Sporobolus are not to be distinguislied as two 

 genera, at least not in regard to the structure of their leaves. 



SjJorobolus is a member of the Agrostkleae, of the subtribe 

 Euagrosteae according to Hacke 1, and has a very characteristic 

 fruit. Its pericarp is thin, dehiscent, free from and merely 

 enclosing the seed; a fruit known in but few other genera, namely, 

 Eleusine, Crypsis and Heleochloa. Many of the species are inha- 

 bitants of open plains and prairies, and are frequently associated 

 with species of Ariatida. The leaves are usually narrow, but Hat 

 with no prominent midrib ; both faces of the blade are furrowed 

 in several species : *S. argutus, brevicnlyx^ crypjtandrus, depauperatus 

 and very deeply in S. aspierifolius, while in the remaining species 

 the Iower face is quite smooth. The leaf surface is mostly scabrous 

 by short papillae, or by long, prickle-like projections as in -S'. cus- 

 pidatus ; glabrous leaves are possessed by *S'. asper, cryptandrus 

 and vaginaeflorus. 



BuUiform cells do not occur above the midrib, but between 

 each two ribs on the upper face of the blade; they are well- 

 developed in S. airoides, argutus^ cryptandrus, depauperatus, indicus 

 and vaginaeflorus, but are more or less reduced in the others, 

 especially in S. pungens, virginicus and junceus. 



The outer cell-wall of epidermis is often heavily thickened on 

 both faces of the blade, and the stomata, which are distributed on 

 both faces of the leaf, are level with the epidermis in most of 

 these species, or slightly projecting (S. brevicalyx and cryptandrus). 



The stereome is relatively but weakly devcloped in Sporobolus, 

 and accompanies the mestome-bundles as small groups on either 

 face of these besides that the outermost portion of the margin 

 contains an isolated bündle of this tissue. Between the ribs, 

 underneath the bulliform cells may be found a colorless tissue of 

 a few, one or two, rows of cells (S. asperifolius, pungens, virginicus), 

 or only near the leaf-margin {S. asper, vaginaeflorus) as a few 

 subepidermal layers on the upper face; in S. junceus the colorless 

 tissue is much farther developed and occurs not only between the 

 ribs, but also above the mestome-bundles and constitutes a verjr 

 prominent portion of the high ridges. 



A somewhat different structure is exhibitcd by S. Hookeriiy 

 which has been studied by Sir r ine andPammel (I.e.), where 

 a larger mass of colorless tissue occupies the upper central portion 

 of the leaf- blade, covering the midrib with its adjoining four 

 mestome-bundles, besides that it occurs also as a few layers 



