10 



BXnJJFORM CELLS. 



The Bulliform Cells are in 



longitudinal, parallel 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 

 Fin. 17.— a. Young stoma of a leaf of usuallymore abundant on the lowcr 



IiHliun rorti; h, older stoma; c, mature 



stoma. 1 xa-,o.-{Sudworth). 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 

 stomuta are found. 



The cells of the bands covering the 

 ma. i xfia- (ii'uvai-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. 



Fio. 18.— Showing a trans- 

 verse section of a very sim- 

 ple leaf. C/i nmaomut i*. min- 



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, which 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 



