476 CONSERVATIVE ORGANS. [LECT. IX. 



until the following spring. During this torpidity, 

 which is maintained throughout the winter, the 

 scales are supposed to preserve the enclosed em- 

 bryo from the effect of cold ; but if we reflect 

 on the insufficiency of so feeble a guard, and 

 further consider the great degree of cold which a 

 seed can withstand without losing its vitality, we 

 shall be able to appreciate justly the value of this 

 opinion. The fact is, the vitality possessed by the 

 embryo in the gem, like that it enjoys in the seed, 

 is not susceptible of the stimulus of heat under a 

 certain degree of temperature; and until it re- 

 ceives this, in combination with circumstances 

 otherwise favourable for vegetation, no change of 

 organization is produced in it, and the vital prin- 

 ciple remains unaffected, even in very low tem- 

 peratures. Nor is this wonderful when we con- 

 sider that a caterpillar may be frozen, and yet 

 live after it has been thawed. But if the gems 

 remained uncovered duiing the long period which 

 intervenes between their formation and evolution, 

 they would run great hazards from the effect of 

 moisture, and from the depredations of insects, 

 against which the scales and the varnishes which 

 cover them are excellent safeguards. We, besides, 

 know that light is unfavourable to the evolution of 

 the embryo in the seed, and may we not conclude 

 from analogy, that this is the case also to the 

 young branch in the gem? 



When the spring returns, and the temperature 



