328 



MANUAL OP BOTANY 



Fig. 702. 



being known as the piliferoics layer. In the roots of Mono- 

 cotyledons and Cryptogams the true epidermis only persists 

 at the apex, forming as before a 

 many-layered root-cap. The rest of 

 the root bears a piliferous layer, but it 

 is in these cases the external layer of 

 the periblem. The external layer of 

 roots is consequently not a true epi- 

 dermis ; it is generally termed the 

 epiblema. 



The cells of the dermatogen are 

 somewhat oblong when seen in section, 

 and are usually rich in protoplasm. 

 As they grow older the walls become 

 thickened, especially on the outer siu:- 

 faoe [fig. 702). Viewed from the surface 

 Fig. 702. TransTerse section of ^j^g present a great variety of outhne. 



the petiole of a species of "^ ^ ^ •' 



Begonia, e. Epidermis with The thickened walls become outicu- 



variable extent, par- 

 ticularly their outer layers. In very 

 thick-walled cells these outer cuticu- 



Generai parenchyma, beioV larised layers can often be stripped off 

 liypoderma. After Sjichs. •^ „ ^ , , , , , 



formmg a sort of detachable structure- 

 less membrane, termed the cuticle (fig. 706). When the cells 

 become adult they lose a great deal of their protoplasmic contents. 

 Fie. 703. Fig. 704. 



r°g°=°^^^©r 



cuticle above and hypoderma i • j . 

 below, the latter formed of iansea 10 a 

 collerichymatous cells cl, c7, 

 with thickened angles v, v. 

 chl. Chlorophyll granules, p. 



"^P^^^S^^m^^^ 



Ol^ 



Fig. 703. Vertical section tbrough the leaf of a Banksia. a, a. Epidermis, 

 c. Spongiform parenchyma, b. Hairs which are contained in little de- 

 pressions on the under surface of the leaf, and at whose base peculiar 

 stomata are found. After Schlelden. — —Fig, 704. Epidermal tissue from 

 the leaf of the Iris (Iris germanica). p^ p. Cuticle. «, «, s. Oval stomata. 

 e, e. Epidermal cells. After Jussieu. 



and are filled with little more than water. The outer layers of 

 the cuticle are often impregnated with wax, which sometimes is 



