GRASSES OF IOWA. 41 



From studies made in the botanical laboratory of the Iowa 

 Agricultural College, the bulliform calls of different species of 

 grass are sufficiently diagnostic in grasses occurring under 

 different climatic and soil conditions, to warrant a study of 

 them. These differences may best be considered by taking 

 some of the different species. Mr. Ball* found that the bulli- 

 form cells of Eragrostis are two or three in number, and in 

 some cases not easily distinguishable from the epidermal 

 cells. 



Mr. Theo. Holm+ says of Leersia oryzoides: "The bulliform 

 cells form grooves between all of the mestome bundles and 

 are of unequal lengths, the middle cells being the largest, with 

 a narrowing towards the surface, thus being nearly triangular 

 in cross sections, the cells on the sides gradually becoming 

 smaller." Both of these species are adapted to hydrophytic 

 conditions and hence the bulliform cells need not be nearly so 

 well developed as in species adapted to dry weather conditions. 

 This is also true to some extent of Panicum proliferum, in which 

 the bulliform cells vary from two to five, usually consisting of 

 one large or two large central cells. In Sporoholus cryptandrus 

 and S. heterolepis the bulliform cells are very nicely developed. 

 According to Miss Emma Sirrine and Mrs. Hansen,]; the bulli- 

 form cells of S. hetrolepis occur in four or five rows, a large 

 central cell and three or four smaller cells on each side. In 

 S. cryptandrus they are somewhat larger than those in S. hetero- 

 lepis. In the latter there are usually two or three quite large 

 cells and two smaller on each side. One or two groups of bulli- 

 form cells occur between a large mestome bundle, and, as in *S^. 

 heterolepis, these do not occur between the last two bundles. In 

 Andropogon scoparius the bulliform cells occur as a continuous 

 row, excepting over the secondary bundles. In Johnson grass 

 the bulliform cells gradually merge into the epidermal cells. 

 The bulliform cells of sugar cane§, which is adapted to the 

 hydrophytic conditions, consist of three or sometimes more 

 rows quite strongly marked. In fact these cells are very much 

 larger than the remaining epidermal cells. 



It may be interesting here to briefly give the structure of 

 the bulliform cells of the various varieties of corn. These 

 have been studied by Mr. Combs. 



*1. c. 



tIFBot. Gazette, 17: 359. 



*1. c. 151. 



§Wm. C. Stubbs. Sugar Oane, 1.2Q.f. G. 8. 



