ORGANIC STRUCTURE. 105 



of early stagnation ; so that although the genial heat 

 of spring revives the dormant plant by liquifying and 

 giving intestine motion to the sap, yet the continu- 

 ance of the growth does not entirely depend on tem- 

 perature. Every hardy plant in this country has only 

 to perfect the shoots, flowers, and fruit which had 

 acquired a certain stage of advancement in the 

 preceding year, and to bring the succession buds to 

 a like stage in this. So in tropical countries the 

 Enkianihus quinqueflora, and the Bombax celba 

 shed their leaves in November, and develope new 

 foliage again in March, notwithstanding the heat of 

 the air is certainly never less than 60. All this goes 

 to prove that the growth of many, perhaps all, plants 

 proceeds by periodical impulses ; their sap being copious 

 or deficient, or transmutable from a thicker to a 

 thinner state, according as the weatner, the season, 

 or the state of the plant requires. 



When the winter repose has taken place, if we 

 examine a transverse section of the second year's 

 shoot, we find it in every respect like that of the 

 seedling ; and if we now look at a cross section of 

 the latter, i. e. the first from the seed, we find it 

 composed of a pith, two concentric layers of wood, a 

 new one formed on the outside of the first, and also 

 a new liber formed within that of the first year ; the 

 cuticle and epidermis still continuing unbroken on 

 the exterior of the whole. Again, in the autumn of 

 the third year, if we examine a cross section of the 

 third or topmost shoot, we shall find it similar to 



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