IOWA ACADEMY OF SCIENCES. 157 



strongly developed only on the upper surface of the leaf; they 

 are much more numerous than in P. capillare, but not nearly 

 so sharply denned. The cuticle (c) is not so strongly developed 

 as in P. capillare. 



The bulliform cells vary from two to five, usually consisting 

 of one large or two large central cells. The leaf is not so 

 strongly involute in this species, but the bulliform cells (b) 

 extend farther down into the mesophyll (mes) than in P. 

 capillare. 



The carene (c 1 ) has one mes tome bundle (m), which is open 

 at the lower side. There are from forty to forty-five mestome 

 bundles in the leaf, the median beiDg the largest. On either 

 side of the carene are five small mestome bundles entirely 

 closed, then occurs a secondary bundle on each side resembling 

 the carene, only much smaller. The leptome is separated 

 from the hadrome in the carene by thick- walled parenchyma 

 cells (p). 



The mestome bundles are of two types; first, such as are 

 open below, and second, those that are entirely closed. The 

 closed are much more numerous than the open; only six or 

 seven open in the whole leaf. The leptome (1) and hadrome 

 (h) are not well developed in the small bundles. 



The mesophyll consists of elongated and somewhat loosely 

 arranged cells of variable size. Oae larger surrounds the 

 chorophyll bearing (cbp) parenchyma cells and comes in con- 

 tact with the stereome (st); the space between the mestome 

 bundles and beneath the bulliform cells is also filled with 

 them. 



The stereome is found on the lower side of all bundles, in 

 contact with the parenchyma and epidermis, and also on the 

 upper surface of all the larger mestome bundles. 



PANICUM CRUS GALLI. 



The most obvious difference between P. crus-gal i and P. 

 capillare is that in this species the leaf is not involute; the 

 epidermal cells (e) are large; the cell wall and cuticle (c) is not 

 so strongly developed but conical projections are found en both 

 surfaces of the leaf. 



The carene has one mestome bundle (m). It differs from 

 the other species studied in that the stereome is not in direct 

 contract with the leptome (1) and hadrome (h) but is separated 

 from them by two rows of thick walled parenchyma (p), while 

 the leptome and hadrome are in direct contact with each other. 



