462 



CONSERVATIVE ORGANS. 



[LECT. ix. 



against the effects of frost, and other accidents of 

 climate to which their situation exposes them. In 

 this climate, however, one of the additional buds 

 is always evolved the same season in which it is 

 protruded. 



Du Hamel first noticed the fact, that stems 

 and branches furnished with 

 alternate axillary gems, have 

 generally one terminal gem 

 only, and those with opposite 

 have generally three terminal 

 gems. In the Horse Chesnut 

 the middle terminal gem is the 

 largest (see a. in the marginal 

 cut), and bursts soonest into 

 foliage; while those on its 

 sides (b. b.) are much smaller, 

 and sometimes never open, but 

 decay and drop from the 

 branch. In the Lilac, on the contrary, the middle 

 terminal gem is always the smallest, and scarcely 

 ever pullulates. In some trees, as for example the 

 Pine tribe, all the gems are terminal. 



The gems on most trees and shrubs rise with a 

 broad base from the surface where they are pro- 

 truded, and, consequently, being in close contact 

 with it, are said to be sessile (sessiles) ; but they 

 are distant or stalked on some; as for example, 

 the common Alder, Alnus glutwosa, on which 



