BOTANY 



sent the appearance of being set in sockets ; while, at the same time, by 

 the multiplication of the cells in the tissue at their base, the whole 

 hair becomes elevated on a column-like protuberance. The hair tapers 

 towards the apex and terminates, somewhat obliquely, in a small head, 

 just below which the wall of the hair remains unthickened. As the 

 wall of the hair is silicified at the end and calcined for the rest of its 

 length, the whole hair is therefore extremely stiff. Such hairs furnish 

 a means of defence against animals. The heads break off at the 

 slightest touch, and the hairs piercing the skin pour out their poisonous 



Fig. 113. — Scale- hair of Asplenium 

 bulbiferum. (X 90.) 



Fig. 114. — Glandular colleter 

 from a stipule of Viola tri- 

 color, showing also a uni- 

 cellular hair, (x 240.) 



contents, which, especially in the case of the Loasnceae, may cause 

 severe inflammation. 



Unicellular Hairs, such as we have so far considered, may 

 terminate in well-defined heads resulting from the swelling of their tips, 

 or their side walls may develop irregular excrescences ; on the other 

 hand, they may remain short and expand like a balloon, or remain 

 close to the surface of the epidermis as spindle-shaped (Fig. 110, .4) 

 or stellate (Fig. 110, 0) hairs. Multicellular hairs may be merely 

 simple rows of similar cells, as the hairs on the stamens of Tradescantia 

 (Fig. 53) ; or their terminal cells may become swollen into globular 

 heads (Fig. Ill), like those on the Chinese Primrose (Primula sinensis) ; 

 or an epidermis may be covered with shield-, star-, or bowl-shaped 

 hairs (Fig. 112). Sometimes the hairs become variously branched, 



