28 SYLVICULTURE. 



of light and air. Here water is transpired and nourishment 

 prepared for further growth by the assimilation of atmospheric 

 carbon and the formation of carbo-hydrates. As the current of 

 sap keeps rising from the roots to the growing-point, a small shoot 

 forms, which aerates the sap and sends it downwards ; and as 

 the elaborated sap descends, woody matter is formed in the 

 centre of the radicle, thus enabling it to ramify, while woody 

 matter is also gradually formed within the vessels of the young 

 plant by the deposition of elaborated matter. The growing- 

 point then acquires the rudimentary form of a leaf, and develops 

 until the first leaves are completely formed to carry on more 

 easily the functions previously performed by the seed-leaves. 

 Assimilation then becomes more vigorous, and the sap is 

 elaborated in larger quantity, conveyed downwards through 

 the cambium, and deposited as cellulose, part being incorporated 

 with the bark, and part forming sapwood. And as the cellular 

 tissue of the stem is also expanding to make room for the matter 

 passing into it, perpendicular and horizontal development go. on 

 simultaneously. Young roots are also formed, which increase 

 and branch by constant gradual increment ; and thus a natural 

 balance is maintained between the root-system and the leaf-area 

 for which water and mineral food have to be provided, and on 

 whose assimilative power increment depends. 



Other leaves appear, all formed like the first, and performing 

 similar functions ; and at last the growing-point or axis ceases 

 to lengthen for the season, and the old leaves wither and fall off. 

 Meanwhile a new set of leaves, instead of expanding after their 

 formation, remain in their rudimentary state, harden, and fold 

 over one another to protect a new growing-point and become the 

 scales of a leaf-bud. 



With the return of warm weather in the second spring the 

 flow of the sap takes place and active vegetation recommences. 

 The buds gradually unfold when the water containing mineral 

 food ascends, and the sap utilised is instantly replaced by 



