ELEMENTARY STRUCTURE. 



51 



Fig. 120. Fig. 121. Fig. 122. Fig. 123. 



Fig. 124. 



Fig. 126. 



Fig. 127. 



Ftg. 120. Stalked unicellular gland of Salvia Fig. 121. Stalked uni- 

 cellular glands of Frogsmouth {Antirrhinum majus) Fig. 122. Stalked 



mauy-celled gland of Ailanthus glandulosa. From Meyen. Fig.1'23. 



Stalked many-celled gland from Begonia pJafani/olia. From Meyen. ■ 



Fig. 124. Many-celled hair of Frogsmouth, terminated by a glandular 



summit, which consists of two secreting cells Fig. 125. Stalked gland 



with four secreting cells. Frcn Meyen Fig. 126. Sessile many-celled 



gland from the common Hop {Ilumulus Lupulus), commonly termed 



lupulinic glands Fig. 127. One-celled sessile glands, termed j^apukp, or 



papilla:. 



they form hardened spherical or other appendages upon the 

 surface of the epidermis, they are termed verruca or warts. 

 When a sessile gland contains an irritating fluid, and is elon- 

 gated above into one or more hair-like processes, which are 

 placed horizontally {fig. 128), or vertically {fig. 129), we ha^-e 

 a sting formed. Stings are sometimes arranged under the head 

 of stalked glands. In the Nettle {fig. 129), the sting consists 

 of a single cell, enlarged at its base 6, by the irritating fluid/, 

 which it contains, and tapering upwards to near the apex, when 

 it again expands into a rounded head s. The enlarged base is 

 closely invested by a dense layer of epidermal cells, w e, which 

 forms a kind of case to it. In touching a nettle lightly, the 

 knob-like head is broken off, and the sharp point of the sting 

 enters the skin, while the irritating fluid is pushed up at the same 

 time into the wound by the pressure thus occasioned, and by the 

 elastic force of the surrounding epidermal cells. If a nettle 

 e2 



