ELEMENTABY STBUCTUEE. 



53 



5. Appendages of the Epideemis. — Upon the surface of tlie 

 epidermis, or in the sub-epidermal tissue, there are frequently 

 to be found certain structures consisting of cells variously com- 

 bined, and containing various substances, which are termed col- 

 lectively Appendages of the Epidermis. We shall treat of them 

 under the two heads of Hairs and Glands. 



1. Hairs. — These are thread-like prolongations externally of 

 the epidermal cells covered by cuticle {figs. 95, g, and 100). 

 They may either consist of a single cell, when they are called 

 simple (figs. 112-116), or of several cells, when they are coynpound 

 {figs. 119 and 120). Simple hairs may be undivided (/t^. 112), 

 or forked {fig. 113), or branched {fig. 114). Avery beautiful 

 form of a simple hair is that called Stellate, as seen in Deutzia 

 scahra, Alyssum, &e. {fig. 115) ; this is formed by a cell dividing 

 horizontally into a number of parts which are arranged in a star- 

 like form (^^. 116). 



Fig. 112. Fig. lis. 



Fig. 11 4. 



Fig. 116. 



Fig. 115. 



Fig. 117. 



Fig. 118. 



IFig. 112. Simple unbranched hair of the common Cabbage. Fig. 113. 

 Forked hair of Whitlow-grass (Draba). Figs. 114 and 115. Branched 

 stellate hairs of Alyssum Fig. 116. Stellate hairs from Althcea offici- 

 nalis. Fig. 117. Branching hair of a species of Marritbium. Fig. 118. 

 Branched hair of Alternantkera axillaris. From Henfrey. 



Compound hairs may be also undivided, as is more frequently 

 the case {fi^s. 119 and 120), or branched {figs. Ill and 118). The 



