122 PROCESS OF NUTRITION. CHAP. III. 



Lateral intimately connected with the sap's ascent. Do 

 cation. Uni " ^e vessels conducting the sap communicate with 

 one another by inosculation or otherwise, so as that 

 a portion of their contents may be conveyed in a 

 lateral direction, and consequently to any part of 

 the plant ; or do they form distinct channels 

 throughout the whole of their extent, having no 

 sort of communication with any other set of tubes, 

 or with one another? 



Denied. Each of the two opinions implied in the question 

 has had its advocates and defenders. At the head 

 of those embracing the former we find Malpighi ; 

 and at the head of those embracing the latter we 

 find Grew ; who, in speaking of what he calls the 

 succiferous and air vessels of the bark and wood 

 of the root, describes them as being no where in- 

 osculated or twisted one about another, but only 

 tangent or collateral.* This was regarded as a proof 

 that the vessels of plants do not communicate la- 

 terally, so as to distribute their sap in all directions, 

 but are destined merely to the nourishment of a 

 particular part. It was also urged in support of 

 the same opinion, that if a tree is planted so as to 

 have cultivated ground on the one side, and uncul- 

 tivated ground on the other, the roots and branches 

 will be the most vigorous and the most luxuriant 

 on the cultivated side; and that if a tree having 

 two or more principal branches, with the same 

 number of principal roots, has one of the roots 

 * Anatomy of Roots, Part II. chap. iii. and iv. 



