N E W P U B L 1 C A T I O N . 77 



This, then, is tiic doctrine of the circulation . Is the doctrine 

 proved I We say, not clearly so. The assumption upon which it 

 is partly founded, is not, to our mind, well established. The as- 

 cending fluid is not water with some saline matter in simple solu- 

 tion ; it is already mucilage long before it reaches the leaf. 

 What is the ascending sap of the sugar maple but mucilage, or a 

 fluid already partially elaborated ? 



2. The analogy between the spongiole of a root and a bladder is 

 assumed also ; for in order that the analogy should hold good, the 

 mucilage in the spongiole should flow out while the water in the 

 earth flows in. This is far from being proved. 



3. No provision is made in this theoretical circulation, for the 

 growth of the branches, or for the flow of sap before the expan- 

 sion of the leaves. 



As our views in relation to the circulation of sap differ some- 

 what from those of our author, we propose in a very few words to 

 give an exposition of them. We must observe, however, that we 

 have never been satisfied with any explanation which we have 

 yet seen. 



Water hokling in solution carbonic acid, together with the saline 

 matters which are common in soils, is received into the spongiole 

 and ascends through the newest parts in the greatest abundance. 

 It partakes of the nature of nutritious matter soon after it is re- 

 ceived into the tissue of the plant. It reaches the dormant bud in 

 which the rudimentary leaves and branch are folded. It furnishes 

 the nutriment whose elaboration now completed in the still imper- 

 fect parts by light, and the leaves are in consequence developed, or 

 in other words grow ; the basal leaves first, the others in succes- 

 sion, and as long as leaves remain whose foundations were laid 

 in the bud the branch elongates, and it seems or appears to elon- 

 gate solely by the development of the leaf at the termination of 

 the branches. In about three or four weeks after the sap begins to 

 rise the branches have attained their full growth ; all this is effect- 

 ed by the ascending sap. While the leaves and branches are thus 

 arriving to maturity the sap only flows feebly downward, but dur- 

 ing this process sap accumulates in the newer parts, especially be 

 tween the bark and wood last formed. Here it becomes pulpy and 

 soft and penetrable. The ascending sap in the mature leaf under- 

 goes those changes which have been so frequent ly described by wri- 



