14 



THE EPIDERMIS. 



excepting very near the tip where there is an ahrupt boat-shaped 

 point. 



On viewing a thin, magnified transverse section of a mature 

 leaf of ScfiJerid ('cnrulea, we see : an outer envelope of cells called 

 the epidermic, e; fihro-vascular lundles, more or less developed ; i, 

 the median bundle, h, h, lateral bundles; groups of long, thick- 

 walled cells in certain places 

 beneath and next to the ep- 

 idermis of the upper and 

 lower sides, called the hy- 

 jmkrmal fibers; a, the lower 

 'median fiber, d, the upper 

 median fiber, c, d, lateral 

 groups of hypodertnal fibers. 

 The other cells are paren- 

 chyma, most of which con- 

 tain granules of chloro- 

 phvll. The vacancv is an 

 air-chamber or canal, la- 



Fia. 14.— Part of a tranaverse section of a leaf , _ 



of SesJcriawcrufea including tlie middle; a, mid- ciOia, i. In aquatlC grasses 

 die hypodermal fibre ; J>, middle flhro-vascular 



bundle; c, d, lateral Kroups of hypodermal flhcrx; +1io«f> oir-plmrnhpra nrp much 

 e, enidermis ; /, huUiform cells, where the l)lade ^'^^^® air-cnamoers are mucu 

 ia closed; (/, the same wliere tlie blade is si)read , 

 open; ?i, ?i, lateral fihro-vascular Imndles; t, air larger, 

 canal, lacuna. 1 x liJO. — ( Duval- Jouve.) 



The Epidermal System consists of : 



a. Epidormis proper. 



i>. liulliform (blister) cells. 



c. 8tomata. 



(f. Trichomes. 



The Epidermis proper consists of a single layer of cells, the 

 length of which seldom very much exceeds three or four times the 

 width or thickness. The two latter dimensions usually are not 

 very dissimilar. 



