158 IOWA ACADEMY OF SCIENCES. 



The mestome bundles are of two types; first, those that 

 resemble the open bundles of other species, only that in this 

 case they are surrounded by thick walled parenchyma outside 

 of which, on two sides occur the chlorophyll bearing paren- 

 chyma cells (c b p); second, those that are entirely closed. 



The mestome bundles are differently arranged in this species, 

 a small mestome bundle occurs beneath the bulliform cells, 

 this bundle is smaller than the one occurring between the bulli- 

 form cells, but is of the same type. Surrounding the bundles 

 of the first type are small chlorophyll bearing cells and more 

 numerous than in the other sj)-3cies studied. The chlorophyll 

 bearing parenchyma cells surrounding those of the second type 

 are larger than those of the first type, but not as large as those 

 of the other type. In this species the leptome and hadrome 

 are in immediate contact while thick walled parenchyma cells 

 surround both. 



The stereome is found on the upper and lower surface of all 

 mestome bundles of the first type and separated from leptome 

 and hadrome by thick walled parenchyma. Stereome does not 

 occur around the mestome bundles beneath the bulliform cells. 

 The mestome bundles between the bulliform cells are always 

 closed below and sometimes entirely so. 



The mesophyll consists of both elongated and round cells 

 bordering on the chlorophyll bearing parenchyma. 



COMPARISON. 



A comparison of the two genera shows that in the genus 

 Sporobolus the cuticle and cell walls are much more strongly 

 developed than in the genus Panicum. 



The mestome bundles in Panicum are more numerous than 

 in Sporobolus. The epidermal cells in Sporobolus are uniform 

 m size, in Panicum variations occur in different species, while 

 in P. crus-galli, the epidermal cells on both sides of the median 

 nerve are smaller than elsewhere on the leaf. 



The bulliform cells are larger and more numerous in Sporo- 

 bolus than in Panicum. 



CONCLUSIONS. 



We feel safe in concluding from our study of these genera 

 that the anatomical characters are marked and constant enough 

 to readily enable one to distinguish the species, and along with 

 the work of others it shows that anatomical characters may be 

 used as a basis for the separation of gpnera and some species. 



