334 



MANUAL OF BOTANY 



and 713). These glandular hairs or external glands may be 

 sessile or stalked. If sessile they present various appearances, 

 and consist of either one secreting cell, or of two or more. 

 Those with one secreting cell placed above the level of the 

 epidermis are frequently termed papillce. 



Hairs with a very large and swollen terminal cell, which 

 serves as a water reservoir, occur upon the surface of the Ice- 



Fici. 712. 



Fig. 71.1 



Fi(j. 712. G-landular hail's from Primula sinensis, a. Young hair. h. Hair 

 showing secretion formed in the cell-wall of the terminal cell. c. Hair 



after discharge of the secretion. Fig, 71^. Glandular hairs from Hop. A. 



Young hair. e. Mature hair. .s.t?. Secretion under the cuticle. Fig.Ti'^. 



Sting of a species of Malpiffhia. c. Epidermis. {/. Glandular appa- 

 ratus. Fig. 715. Sting of the common Nettle ( Urtica dioica)^ consisting 



of a single cell with a bulbous expansion at its base, 6, and terminated 

 above by a s^velling, s, and containing a granular irritating fluid, /, /. 

 tr ''.'Epidermal cells surrounding its base. 



plant [Mesenibryanthemum crystalKnum), and it is to their 

 presence that the peculiar appearance of that plant is due. 



"When a sessile gland contains an irritating fluid, and is 

 prolonged above into one or more hair-like processes, which 

 are placed horizontally {fiff. 714), or vertically (fig. 715), \\v 

 have a sting formed. 



In the Nettle ijig. 715) the sting consists of a single ceU, 



