78 QUARTERLY JOURNAL. 



ters upon physiology, and then passes through the inosculating ves- 

 sels between the upper and under surface of the leaf and circulates 

 downwards, or the full flow downwards is now established and its 

 progress deposits the matter which is to form the next annual 

 layer, which is in fact nothing more than a fibre or root proceed- 

 ing from each leaf, penetrating through the already formed pulpy 

 matter of the ascending sap. It, however, descends, passes 

 into the root, where it deposits the matter which is to elongate 

 this part of the plant. The whole end of the circulation is this : 

 by the ascending fluid the buds become leaves and branches ; by 

 the descending aliment the roots extend outwards and downwards, 

 while both currents assist in the formation of the annual layers. 



This exposition, however, leaves out of view the special force 

 by w^hich the currents were moved, and it is rather a statement of 

 what is effected by the ascending and descending fluids. The roots 

 may require the elaborated sap, that which has undergone a change 

 in daylight. 



But there are many instances where the woody fibre is formed 

 by the descending sap — the pandamus, for example ; and then 

 there are still other cases where a tree has survived accident, and 

 has increased in diameter by the descending fluid. Thus, when 

 the entire bark, near the root, has been destroyed, we have seen 

 it survive the injury, the whole root, together with an inch or two 

 of the trunk being in a state of perfect dryness, like a piece of 

 seasoned wood, and yet the upper part w^as covered with leaves, 

 and several annual layers were already deposited down to the in- 

 jured part. It is evident, then, that plants possess the power of 

 accommodating themselves to circumstances, and their circulation 

 will go on though not a spongiole exists, or a root from which a 

 spongiole can spring. 



A tree from which a ring of baik four or five inches long has 

 been removed, will frequently survive the injury, and its trunk, 

 both above and below the removed ring, wall increase in diame- 

 ter. Two pine trees opposite the cantonement at Plattsburgh, are 

 still standing and growing in this condition. The growth upon 

 the lower margin is upwards, and laps upon the dry portion of the 

 ringed part, so that should those trees continue to live and grow, 

 this part will entirely close up by a deposition from below, while 

 not a single layer is deposited upon the apparently dead part at 



