THE EPIDERMAL SYSTEM. 



97 



cells are so transformed into a secreting organ, 

 tion appears as a rounded 

 pustule, partly surround- 

 ing the secreting cell 

 (Figs. 83 to 87), and 

 which is removed 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 

 Primula einehm, ia several stages of develop- 

 ment, a, the beginning of the secretion iu trie 

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

 creted matter ; d, an old hair after the removal 

 of the secreted matter. X 142.— After De Bary. 



(a) Tricliomes are, in gene- 

 ral, easy objects of study. 

 In many cases tliey may be 

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



Fis.84. 



Pis. 85. 



Fig. 86. 



Via. 87. 



Fig. 84.-0', the cell a of Fig. 8.3more highly magnified ; a" the same after 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 ; (/, the same after 

 treatment with alcohol, x 875.— After De Bary. 



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

 ments of the secretion pustule surrounding the terminal 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 out 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 142.— After De Bary. 



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

 closed air. 



