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for a particular purpose, they are stripped off a tree when in 

 a growing state, as is done in the mulberry, or if the hail 

 destroy them when the tree is in full vigour, a vital phenome- 

 non ensues which partly repairs the injury ; all the latent 

 buds in the axils, which would not have been developed till 

 the following year, grow very rapidly and form new leaves, 

 and if by any particular circumstance this phenomenon does 

 not take place, the tree usually perishes. Vegetables effect 

 many changes in the food they take up through the leaves; 

 as when many different kinds of fruit are produced by grafts 

 from the same stock. All distribution of the leaves is con- 

 nected with the functions of the organs ; and in order that 

 the action of each may be properly performed, it is necessary 

 either that the leaves be far apart from each other, or that, 

 within a given distance, they cover each other as little as 

 possible ; in fact it will be seen that in all the different 

 systems of the position of the leaves, it results that those 

 which arise immediately above the others, never exactly cover 

 them — in the least favourable cases the third covers the first, 

 and the fourth the second ; in several others it is the sixteenth 

 or sometimes the fifteenth or twentieth which covers the first. 

 Leaves, in presenting to the winds two resisting surfaces, 

 more or less considerable, tend to produce an almost con- 

 tinual agitation in the branches of trees ; and we know from 

 some beautiful experiments of Mr. Knight, that the branches 

 facilitate the progress of the sap and the growth of the 

 trunk : trees with large leaves grow more rapidly, and serve 

 for the secretion of different juices. 



I have so long dwelt upon the leaves to impress upon man- 

 kind, if possible, their value, and the more so considering that 

 they are in general scarcely thought of any value. Every leaf 

 bears a bud in its axil, and every bud^ the rudiment of a new 

 branch. The bud is placed at the summit of a fibre, and 

 communicates with the medullary sheath by the medullary 



