TRAKSPIRA TIOX. 



41 



and should he then mounted in water for microscopic examina- 

 tion.* 



80. Epidermis of the leaf. — In this section we see that the 

 green jiart of the leaf is bordered on what are its upper and 

 lower surfaces by a row of cells which 

 possess no green color. The walls of 

 the cells of each row have nearh par- 

 allel sides, and the cross walls are per- 

 pendicular. These cells form a single 

 layer o\-er both surfaces of the leaf and 

 are termed the epidermis. Their walls 

 are quite stout and the outer walls are 

 culicularized. 



81. Soft tissue of the leaf. — The 

 cells which contain the green chloro- 

 phyll bodies are arranged in two dif- r. . ^'^' ^°' 



.Section through i\y leaf shoT^ing 



ferent \YayS. Those on the upper side comiriunicationbMweenstoraateand 



^ ^^ the large intercellular spaces of the 



of the leaf are usually long and pris- '^^^^ stoma cioseii. 



matic in form and lie closely parallel to each other. Because of 



thi^ arrangement of these cells they are termed the /a&aa'e cells, 



and form what is called the palisade layer. The other green 



cells, lying below, 



vary greatly in size in 



different plants and to 



some extent also in the 



same plant. Here we 



... notice that they are 



Fig. SI- f-ig-s^- •' 



Stoma open. Stoma closed. elongated. Or 0\"al, Or 



Figs. 34. 35^Section through stomata of ivy leaf. somewhat irretjular in 

 form. The most striking peculiarity, however, in their arrange- 

 ment is that they are not usually packed closely together, but each 

 cell touches the other adjacent cells only at certain points. This 

 arrangement of these cells forms quite large spaces between them, 

 the intercellular spaces. If we should examine such a section of 

 a leaf before it is mounted in water we would see that the inter- 

 * Demonstrations may be made with prepared sections of leaves. 



