CH. VII.] 



THE FRUIT AND SEED. 



217 



considered. These circumstances, so far as the roots 

 and leaves were also concerned, have heen examined 

 in previous chapters. 



Sap. — The more rapidly and consequently the 

 greater the amount of this poui-ed into the branches, 

 the greater suiface of leaf is required for its elabora- 

 tion ; and, as the plant has power given it of increas- 

 ing most freely, and even at the expense of others, 

 those organs which are most necessary, the leaves of 

 such abundantly supplied branches are increased 

 both in number and size, whilst the blossom is pro- 

 portionately dimmished in number, or is obliterated 

 entirely. A plant propels its sap with greatest force 

 perpendicularly, so much so that the sap rising in a 

 vine branch growing in a right line from the root with 

 a force capable of sustaining a column of mercuiy 

 twenty-eight inches high, will, if the branch be bent 

 do^\Ti to a right angle, support 

 barely twenty-three inches, and if 

 bent a few degrees below the hori- 

 zontal, the column sustained will 

 not be more than tv/enty one 

 inches. This is the reason why, at 

 such angles, gardeners find the 

 trained branches of their wall trees 

 rendered more productive of blos- 

 soms, and furnished with a smaller 

 smface of leaves. A similar effect 



