BY K. BKEAKWELL. 



391 



(3.) The epidermal cells on the superior surface have subimposed 

 two, three, and sometimes four layers of similar uncoloured paren- 

 chymatous cells. 



(4.) No stomata can be perceived on the superior surface. 



(5.) A girdle-canal is present. 



From an anatomical standpoint, the species under discussion 



may be divided into three groups, viz. : — 



(Andropogon iiiterniedius. 



Group \.\A. affinis. 



\.A. sericeus. 



Group ii. Andropogon ischcetnum. 



^ ... (Andropogon refr actus. 



Group in.- ^ . ,. 



l^. intermedium. 



In considering the first group, it may be seen that there are 

 certain well defined points of difference between A. intermedius 

 and the other two species ; and also less defined differences 

 between A. affinis and A. sericeus. In A. intermedius^ there are 

 more primary bundles in the midrib, than in A. affinis or A. 

 sericeus. The intermediate bundles, with a corresponding de- 

 velopment of sclerenchyma, are also more numerous than those 

 of the other two species; and the bulliform cells are not as 

 distinctly fan-shaped. A. sericeus differs from A. affinis only in 

 the slightly greater development of the sclerenchyma, and in 

 the slightly greater number of bulliform cells in each series. 



A. ischcemum differs from the first group in the much greater 

 development of the sclerenchymatous tissue, which, however, is 

 not as great as that of the third group. The cuticle is also much 

 thicker, on both the superior and inferior surfaces, than that of 

 the previous species. Another characteristic difference is the 

 nature of the vascular bundles, which are much more numerous, 

 and more densely crowded than in any of the other species. 



A. refractus and A. homhyci^ius differ widely from any of the 

 species of the other two groups. The extreme development of 

 sclerenchymatous tissue, the thick nature of the cuticle on both 

 the superior and inferior surfaces, and the arrangement of 

 stomata in grooves on the inferior surface, are well marked 

 characteristics, which are not seen in any of the other species. 



