14 



THE EPIDERMIS. 



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

 point. 



On viewing a thin, magnified transverse section of a mature 

 leaf of Sesleria ccerulea, we see : an outer envelope of cells called 

 the epidermis, e; fibro-vascular bundles, more or less developed ; ~b, 

 the median bundle, h, h, lateral bundle's : 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- 

 podermal fibers; a, the lower 

 median fiber, d, the upper 

 median fiber, c, d, lateral 

 groups of hypodermal -fibers. 

 The other cells are paren- 

 chyma, most of which con- 

 tain granules of chloro- 

 phyll. The vacancy is an 

 air-chamber or canal, la- 



Fio. 14. Part of a transverse section of a leaf 



of Sesleria ccei-ulea including the middle; a, mid- cuild, I. Ill aquatic grasses 

 die hypodermal fibre ; b, middle fibro-vancular 



bundle; c, d, lateral groups of hypodermal fibers; 4-KaQa oi-p plinmbprs arp much 

 e, epidermis ; /, buMiform, cells, where the blade these air-CliamDerS are 

 is closed ; g, tlie same where the blade is spread , 

 open ; h, h, lateral tibm-vascular bundles ; t, air larger, 

 canal, lacuna. 1 x 130. (Duval-Jouve.) 



The Epidermal System consists of : , 



a. Epidermis proper. 



b. Bulliform (blister) cells. 



c. Stomata. 



d. 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. 



