MOVEMENTS OF CONSTRUCTIVE MATERIALS. 



359 



itself densely filled with proteid substances, in which the extremely small quantity 

 of cell-wall forming substance eludes direct recognition. 



So far as we are informed with respect to the corresponding matters in trees and 

 other woody plants, the movements referred to take place here also practically 

 along the paths indicated, though with some slight modifications. Here, however, 

 the additional fact comes into consideration that the parenchymatous tissue 

 system extends also into the wood ; from the cortex the horizontal medullary rays 

 lead directly into the interior of the compact mass of wood, and the wood paren- 

 chyma distributed between the proper wood-fibres and vessels is proved to be in 

 continuity with them, so that medullary rays and wood-parenchyma may be regarded 

 to a certain extent as fine ramifications of the cortical parenchyma, by means of 

 which it extends into the compact mass of 

 wood. Accordingly, during the vegetative 

 period this parenchymatous part of the 

 wood also becomes filled with reserve- 

 materials ; chiefly, and usually in our trees, 

 with starch, in some cases also with other 

 cell-wall forming substances- -in the North 

 American Sugar-maple for example with 

 cane-sugar. That these reserve-materials 

 stored up in the wood are dissolved when 

 the buds are put forth in spring, and 

 carried away and used up in growth, fol- 

 lows from their disappearance at that time; 

 this proceeds from the thinner bud-bearing 

 twigs to the older branches, and then 

 into the stem, as stated some time ago 

 by Theodore Hartig. This distinguished 

 observer found also that when in the 

 spring a ring of cortical tissue is taken from 

 the stem, and the whole of the ordinary 

 conducting organs thus interrupted, the 

 tree nevertheless puts forth shoots, and 

 makes use of the starch deposited in the 

 wood parenchyma beneath the annular 

 wound in the process, whence it follows that this starch can be conveyed through 

 the wood parenchyma itself. It is easy to demonstrate by micro-chemical investiga- 

 tions as well as by simple experiments^ that the buds of trees behave exactly like 

 the germinal shoots of tubers, bulbs, and seeds, with respect to the phenomena here 

 spoken of. 



I have hitherto taken into consideration only the vegetative organs — roots and 

 shoots. That exactly the same principles hold good for the nutrition of flowers and 

 fruits, so far as the employment and the travelling of plastic substances in growth are 

 concerned, is a fact of which I afforded a series of detailed proofs in my researches 



Fig. 241.— Winter-bud of the Horse-chestnut in longitu. 

 dinal section, r cortex, k wood, ;« pith of the previous year's 

 shoot-axis -vr. s scales, I foHage I 

 tains the inflorescence *. 



I'es of the bud which ( 



* See note 2, p. 355. 



