FUNCTION.] GENERAL CONSIDERATIONS. 135 



leaves, is covered from end to end with little, symmetrically 

 arranged, projecting bodies, which are the buds. 



The cause of the figure of the perfect shoot being conical 

 is, that, as the wood originates in the base of the leaves, 

 the lower end of the shoot, which has the greatest number of 

 strata, because it has the greatest number of leaves above it, 

 will be the thickest ; and the upper end, which has had the 

 fewest leaves to distend it by their deposit, will have the least 

 diameter. Thus that part of the stem which has two leaves 

 above it will have wood formed by two successive deposits ; 

 that which has nine leaves above it will have wood formed by 

 nine successive deposits ; and so on : while the growing point, 

 as it can have no deposit of matter from above, will have no 

 wood, the extremity being merely covered by the rudiments of 

 leaves hereafter to be developed. 



If at this time a cross section be examined, it will be found- 

 that the interior is no longer imperfectly divided into two 

 portions, namely, pith and skin, as it was when first examined 

 in the same way, but that it has distinctly two internal, per- 

 fect concentric lines, the outer indicating a separation of the 

 bark from the wood : and the inner, a separation of the wood 

 from the pith : the latter, too, which in the first observation 

 was fleshy, and saturated with humidity, is become distinctly 

 cellular, and altogether or nearly dry. 



III. With the spring of the second year, and the return of 

 warm weather, vegetation recommences. 



The uppermost, and perhaps some other, buds, which were 

 formed the previous year, gradually unfold, and pump up sap 

 from the stock remaining in store about them ; the place of 

 the sap so removed is instantly supplied by that which is next 

 it ; an impulse is thus given to the fluids from the summit to 

 the roots ; fresh extension and fresh fibrils are given to the 

 roots ; new sap is absorbed from the earth, and sent upwards 

 through the wood of last year; and the phenomenon called 

 the flow of the sap is fully completed, to continue with greater 

 or less velocity till the return of winter. The growing point 

 lengthens upwards, forming leaves and buds in the same way 

 as the parent shoot : a horizontal increase of the whole of the 



