196 



CASSELL'S POPULAR GARDENINa. 



available nutriment. Just beneath, the skin of a 

 human being, or of any animal, there is a thin layer 

 of granules of fat, capable of being used in the nutri- 

 tion of the body, and deposited for that purpose. 

 So it is with ordinary trees or shrubs. Just be- 

 neath the outer layers of the rind or bark, which 

 are mostly dead, there is a layer filled with nutri- 

 tive matter — abundantly so in late autumn and 

 winter, less markedly so in spring and summer, 



Fig. 20. — Expanding Bud of Horse-Chestnut, showing the 

 bud-scales which fall off as the leaves develop. 



while growth is going on actively, and there is a 

 brisk call on the resources of the plant. 



It is found, moreover, by anatomists, that the buds 

 originate in the vicinity of this food-layer ; they do 

 not spring from the deeper central portions of the 

 stem, but from the portions nearer to the surface. 

 The operation of budding affords a familiar illustra- 

 tion of this. In this process a bud from one plant is 

 implanted beneath the bark of another, care being 

 taken not to cut the stem too deeply, but only to the 

 level of the food-layer, in the immediate vicinity of 

 or actually in which the bud is implanted, (See Figs. 

 22, 23, also page 233.) In this case, then, the transit 



of food and fuel to the machine requiring it is a short 

 one. The bud, like the seedling plant, is thus at hrst 

 dependent on the funded capital reserved for its use. 

 That capital may roughly be compared to bullion ; 

 before it can be realised and rendered available for 

 use, it has to be coined, and this process of convert- 

 ing bullion into coin is, as it was in the case of the 

 seed, the conversion of the insoluble into the soluble 

 — a conversion effected, it is to be presumed, in the 

 same manner and by the same agency as already de- 



Fig 21.— Leaf-bud of the Poplar. 



scribed in the case of the seed. Before any part of 

 the plant, seed, or bud can earn an income for itself, 

 it is necessarily dependent on stored-up capital. It 

 uses up that capital in the formation of new growths 

 and in the development of force, as we shall here- 

 after see. The relations and the due proportion that 

 capital, income, and expenditure bear one to the 

 other, require to be, and are, adjusted by the living 

 plant with the utmost nicety. The business of the 

 physiologist is to find out as much as he possibly can 

 of these complicated but all-important relations, and 

 of the circumstances, external or in the plant itself, 

 which control or modify them. It is the business 

 of the gardener to turn the information so acquired 

 to practical use. 



