C 230 ] 



And his experiments on the crossing of wheat, 

 which is very easi'y effected, merely by sowing the 

 different kinds together, lead to a result which is of 

 considerable importance. He says, in the Philosophi- 

 cal Transactions for 1799, " in the years 1795 and 

 1796, when almost the whole crop of corn in the 

 Island was blighted, the varieties obtained by crossing 

 alone escaped though sown in several soils, and in very 

 different situations." 



The processes of gardening for increasing the 

 number of fruit-bearing branches, and for improving 

 the fruit upon particular branches, will all admit of 

 elucidation from the principles that have been advan- 

 ced in this Lecture. 



By making trees espaliers, the force of gravity is 

 particularly directed towards the lateral parts of the 

 branches, and more sap determined towards the fruit 

 buds ; and hence they are more likely to bear when 

 in a horizontal than when in a vertical position. 



The twisting of a wire, or tying a thread round 

 a branch has been often recommended as a means of 

 making it produce fruit. In this case the descent of 

 the sap in the bark must be impeded above the liga- 

 ture ; and more nutritive matter consequently retain- 

 ed and applied to the expanding parts. 



In engrafting, the vessels of the bark of the stock 

 and the graft cannot so perfectly come in contact as 

 the alburnous vessels, which are as much more nu- 

 merous, and equally distributed ; hence the circulation 

 downwards is probably impeded, and the tendency 

 of the graft to evolve its fruit-bearing buds increased. 



