16 



BULLIFORM CELLS. 



The Bulliform Cells are in 



longitudinal, jDarallel lines; they 

 are larger and extend further into 

 the leaf than ordinary epidermal 

 cells. 



Where the epidermis covers the 

 hypodermal fibers, it consists of 

 long, thick-walled cells, which are 

 Fig. 17.— a, Young stoma of a leaf of usuallymorc abundant on the lower 



Indian corn; h, older stoma; c, mature 



stoma. ix35o.-(Sudwdrth). than on the upper surface. Some- 



times they are reduced to two small rows, or rarely disappear 

 entirely. Sometimes the hypodermal fibers 

 cover all the lower side of a leaf, as in many 

 species of Festuca. In such cases there may 

 be none, a few, or many on the upper side, 

 or it may be entirely covered, excepting a 



few lines on the sides of the veins where the 

 stomata are found. 



Tig. 18.— Showing a trans- rni n j? j_t i t • j.i 



verse section of a very Sim- ihe cclls 01 the bands covering the 



pie leaf. Vnlamayrrmtii^min- 



ima. 1^50— (Duvai-Jouve.') parenchyma are larger than those which are 

 over the veins or hypodermal fibres. On the upper surface of the 

 leaf, these bands are often cut in two by bulliform cells. 



The Stomata (small mouths) are in regular rows, placed 

 longitudinally on. certain parts of the leaf, and are always devel- 

 oped over a small cavity. The plan seems to be the same for all 

 grasses. In some species the stomata are all above, in others all 

 below, while some have them on both sides. 



Trichomes. — Some single cells or groups of cells of the epi- 

 dermis, extend and become trichomes, Avhich are straight or 

 curved, stout or feeble. They are real epidermal cells, and are 

 not prolongations from the outer part of a cell, as is the case 



