206 SPRING. 



it begins to act, or downward again in the summer 

 when the leaves and flowers are perfect, and the cam- 

 bium begins to consolidate ; and we have all the ap- 

 pearances against such a circulation. We are aware 

 that Dr. Hales found the force with which the sap 

 flowed from a cut vine, upwards, was equal to thirty- 

 eight ounces of mercury, or about twenty pounds on 

 the square inch ; but though that certainly proved 

 that the sap had a tendency upward to that amount, 

 it proved no circulation. If the vine had not been 

 cut, it would have pushed its twigs and tendrils to the 

 weight of perhaps twenty feet in the course of the 

 season ; but had it been left to do so, we are not war- 

 ranted in saying that the sap would have flowed up- 

 wards at the same rate. The elongation that takes 

 place by the new shoot, whether that be upwards or 

 lateral, is not any thing that comes originally from the 

 root. It is always the development of something that 

 is already there; there is always a bud, often a cluster 

 of buds, and there is often a little collet around the base 

 of the bud, containing a store of gems of buds in an 

 undeveloped state. We may lay it down as a general 

 principle, therefore, that that which is developed by 

 the annual action of the tree, does not come to the 

 place where it is developed by any circulation, but is 

 produced just where it is found ; and, though the spe- 

 cific operations of leaves and roots are not very well 

 known, and are most likely different in different states 

 of the weather or the plant, there are no proofs of a 

 circulation from the one to the other, either upwards or 

 downwards. If the energy come from the roots, it 



