14 



THE EPIDERMIS. 



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

 point. 



On viewing a thin, magnified transverse section of a matnre 

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

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

 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- 

 jjodermal -fibers; a, tlie lower 

 median fiber, d, the upper 

 median fiber, c, d, lateral 

 o-roups of liypodermal fibers. 

 The other cells are paren- 

 chyma, most of which con- 

 tain granules of chloro- 

 phyll. The vacancy is an 

 air-chamber or canal, ia- 



Fig. 14.— Part of a transverse section of a leaf . _ . 



of i>6s(criacffi7M(ea including the middle; a, mid- cuua, i. In aquatlC graSSCS 

 die hypodermal tibre ; ft, middle fihro-vcutcular 



tmndle; c, d, lateral groups of hupodermal lihers; +\^QgQ air-cliambers are niucll 

 €, epidermis; /, /<((»i;or/n cells, where the blade 

 Is closed; y, the same where the blade is spread , 

 open; ?i, /i, lateral Jihrd-vascidar iHoidles; i, air larger, 

 canal, lacuna. 1 xliiu. — (Duval-Jouve.) 



The Epidermal System consists of: 



a. Epidermis proper. 



i. Bulliform (blister) cells. 



c. Stomata. 



</. Trichomes. 



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

 length of wliieh seldoiu very much exceeds three or four times the 

 widtli or thickness. Tlit- two latter dimensions usually are not 

 very dissimilar. 



