156 IOWA ACADEMY OF SCIENCES. 



plainly shows that it can adapt itself to di-fferent conditions of 

 soil and moisture. 



PANICUM CAPILLARE. 



This species has a hairy appearance and is harsh to the 

 touch. The epidermal cells (e) are large, the cuticle (c) and 

 epidermal cell walls are thicker than in P. crus-galli and P. 

 proliferum, but not so well developed as in the genus Sporobolus. 

 The walls of the epidermal cells of the upper and lower sur- 

 face of the leaf have small conical projections (cp). The end 

 of the leaf terminates in a small thickened point; on the edges 

 of leaf occurs a buudle of stereome (st). 



The buUiform cells do not vary much from the epidermal 

 cells, they are somewhat larger, however, and vary in number 

 from three to five, the middle cell being the largest. The 

 carene (c') has one mestome bundle (m) differing from those of 

 secondary veins only in that it is larger, and beicg open on 

 both upper and lower side. The mestome bundles are of three 

 types: first, those which are open both above and below, second, 

 those which are open below, and third, those which are closed. 

 The leptome (1) is separated from hadrome (h) by thick walled 

 parenchyma (p). In this species the arrangement of mestom.e 

 bundles is irregular, the number varies from forty to fortj'-- 

 three bundles in one leaf. There are from twenty to twenty- 

 two bundles on each side of the carene, and of these, three on 

 each side are of the first type, three of the second type and the 

 remaining of the third type. In the closed mestome bundles 

 the leptome and hadrome are not so well developed as in 

 those which are open. The stereome occurs on the upper and 

 lower surface of all open mestome bundles, while in those 

 which are closed it is found sometimes on the upper surface 

 and sometimes on the lower surface, and sometimes it is entirely 

 wanting. It consists of from two to four rows, bordering 

 immediately on the chlorophyll bearing parenchyma (c b p). 

 At the sides of the leaf well developed stereome occurs for the 

 purpose of protection. 



The mesophyll (mes) consists of elongated cells joining the 

 chlorophyll bearing parenchyma. Between the mestome 

 bundles surrounded by the mesophyll, we have colorless 

 parenchyma. 



PANICUM PROLIFERUM. 



In this species the epidermal cells are much smaller than in 

 P. capillare, and the conical projections (c p) are found more 



