BY MAR.TORIE ISABKL COLLINS. 



251 



increase as the leaf-surface increases in area by the differentia- 

 tion of the leaf-tissues. Tn the older leaves, the glands lose 

 their activity, except as mentioned above, in that region where 

 the leaf-base clasps the stem. There, the glands remain active 

 throughout the life of the leaf. A section through this region 

 shows an abundant development of glandular hairs of the same 

 nature as those on the young leaves. By the activity of these 

 glands, the axils of the leaves are filled with secretion, and pro- 

 vision is made for the protection of the axillary buds. At the 

 junction of the stem and leaf-base is a circlet of long, multi- 

 cellular clothing-hairs (PI. xxvii., fig 2;. These were tested for 

 resin and mucilage, with negative result. 



The Development of the Glands. 

 That the glands are hairs, is evinced in the manner of their 

 origin from a single epidermal cell. Any epidermal cell may 

 form a gland. The- cell enlarges, the nucleus divides, and a 

 horizontal wall is formed separating two cells, the uppermost of 

 which becomes considerably enlarged and spherical in outline 

 (Text-fig. 1, a). A second, horizontal wall cuts off the rudiment 



Text-fig. 1. — Stages (a-g) in the development of the glandular hairs; ( x 530). 

 of the .stalk at the base of the spherical cell, which latter is 

 destined to become the head-cell of the gland (Text-fig. 1,6). At 

 this stage, either a second stalk-cell is formed (Text-fig. l,c>, fol- 



