94 AGE AT WHICH PLANTS CAN BEAR FKUIT. 



of a tree is ringed,* it ceases to he sterile ; and this can only 

 be accounted for upon the supposition that the secreted matter 

 of the branch, instead of being conveyed away into the trunk 

 and roots, is stopped by the annular incision, above which it is 

 compelled to accumulate. If a tree that is unproductive be 

 transplanted, it begins to bear; in this case the operation 

 injures its roots, sap is therefore less abundantly supplied in the 

 succeeding season to the leaves ; the leaves are therefore less 

 able to grow than they previously were, and they consequently 

 do not consume the nutritious matter lying in the branches, and 

 which they would have expended, had they been able to grow 

 with their former vigour ; hence the nutritious matter accumu- 

 lates, and flower-buds are formed. In this country, if a fruit- 

 tree has its crop destroyed one year, it bears the more abun- 

 dantly the next ; owing, no doubt, to the accumulation in its 

 system of that nutritive matter which would not have been 

 present there, had the crop which was destroyed been allowed 

 to grow : and the reverse of this is well known to be the fact ; 

 an excessive crop one year being followed by a scanty crop the 

 succeeding year. So, when a young seedling fruit-tree is 

 made to bear prematurely by grafting it upon an old stock, the 

 effect of which will apparently not be to diminish its vigour, it 

 may be conceived that, in the first place, the seedling will 

 receive a considerable quantity of nutritive matter from the old 

 stock, where it had been already collected, and that thus the 

 supply will be greater than the consumption, however large the 

 latter may be ; and, secondly, that, at the time of union of 

 itself with the stock, there will be sufficient interruption of 

 continuity in the bark to oppose some obstacle to the descent 

 from the seedling of whatever matter it may have received or 



* One of the effects of ringing tas been otserved to consist in the formation of 

 numerous barren shoots below the wound, while fertile shoots appear above it. This 

 is conformable to the theory of the formation of flowers being determined by a super- 

 abundance of nutritious matter in a given place. The bark below the annular excision 

 is out off from a supply of the sap elaborated by the leaves above it ; and, at the same 

 time, in consequence of the obstruction of the wound to the ascent of the crude sap, 

 an unusual supply of the latter is forced towards the buds in the bark below the 

 wound, which buds, being chiefly fed with oi-ude sap, push forth into branches and 

 leaves, but bear no flowers. 



