TRE EPIDERMAL SXS'rjuM. 



97 



'Cells are so transformed into a secreting organ, 

 tion appears as a rounded 

 pustule, partly surround- 

 ing the secreting cell 

 (Pigs. 83 to 87), and 

 "which is remoyed upon 

 the slightest touch. Tri- 

 chomes of this nature are 

 called glandular hairs ; 

 they are exceedingly vari- 

 able in form, and are not 

 infrequently short and 

 depressed, when they are 

 known as surface glands, 

 or glandular scales (Fig. 

 87). 



The secre- 



Fig. 83.— Glandular hairs from the petiole of 

 Priimda sinensis, in several stages of develop- 

 ment, a, the beo:inning of the secretion in the 

 terminal cell; ft, hair with a large mass of se- 

 creted matter ; d, an old hair after thg removal 

 of the secreted matter. X 148.— After De Bary. 



(a) Trichomes are, in gene- 

 ral, easy objects of study. 

 In many cases they may be 

 simply scraped off and mounted in alcohol, or in a solution of potash 



Fig. 84. 



Fia. 85. 



Fie. 86. 



Fig. 87. 



Fig. 84. —a', the cell a of Fig. 83more highly magnified ; a" the same alter removal 

 of the secretion by treatment with alcohol. X 375.— After De Bary. 



Fig. 85 —c, end of a hair with large mass of secreted matter ; c', the same after 

 treatment with alcohol. X 375.— After De Bary. 



Fig. 86.— The end of the hair d, in Fig. 83, more highly magniiled, showing the frag- 

 ments of the secretion pustule surrounding the termmal cell, which still contains pro- 

 toplasm. X 375.— After De Bary. 



Fig. 87.— Glandular scale from the hop. A, in its young stage ; B, the same some 

 time afterward— the secretion from "the cells has pushed oat the cuticle and filled the 

 space between it and the cells (in the specimen from which these were drawn the 

 secretion was removed by solution. in alcohol). X 143.— After DeiBary, 



. after wetting them with alcohol to free them from entangled and en- 

 closed air. 



