V] EPICORMIC BRANCHES 59 



supplies may bring about the death of the bud, and the 

 same result will follow if the slender conduits for water 

 and supplies w are severed so as to cut off the bud from 

 its connections with the general vascular system. 



If, now, from any cause whatsoever, the upper parts 

 of the tree begin to make less strenuous calls on the 

 general supplies of water and food-materials in the wood- 

 system W, or if the foliage as a whole is suddenly enabled 

 to supply more food-materials and to attract more water 

 into this wood-system, then the bud B has an opportunity 

 of obtaining a larger share of supplies than was hitherto 

 the case, and can forthwith put out a shoot on its own 

 account, the leaves on which will henceforth afford sup- 

 plies sufficient for the further development of such shoot, 

 and of the buds formed on it, and thus establish it as 

 a perfectly normal but belated member of the branch- 

 system. 



It is easy to see what circumstances may bring about 

 these events : the cessation of growth in height as the 

 tree reaches its maximum stature ; the dying off of the 

 uppermost twigs during a drought ; a serious wind- 

 breakage or fractures from heavy loads of snow or ice ; 

 all or any of these would lead to a diminution of the 

 upward draught of the supplies in the wood at W, and so 

 leave more to spare for the feeble draught exerted by 

 the bud conduits at w. On the other hand, a sudden access 

 of increased light and air to the crown of the tree, con- 

 sequent on the removal of neighbouring trees, would have 

 two principal results : increased supplies of water from 

 the roots, owing to the removal from competition of the 

 roots of the absent trees, and increased supplies of food- 

 materials from the now better illuminated and aerated 

 leaves, so that again there would be more to spare for 

 the bud B. 



