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the angle of the ramification of" the tree and the angle of venation of 

 the leaf. The following table gives the results of numerous measure- 

 ments of the angles of branching and venation, where these were 

 found to agree : — 



We have made a sufficient number of measurements to be able to say 

 that there is often such a correspondence. But it should be acknow- 

 ledged, that while it is not difficult to determine the angle of the ve- 

 nation of the leaf, it is most difficult to determine what is the normal 

 ramification of the tree, for the angle at which the branch goes off is 

 liable to be modified by a great number of circumstances. All that 

 we argue for is a general correspondence between the tendency of the 

 direction of the branches and the tendency of the direction of the 

 veins of the leafage, — a tendency liable, however, to be affected by a 

 great number of circumstances, natural and artificial. It does not 

 follow, because there is a correspondenco between the venation of the 

 leaf and the ramification of the tree, that therefore the two — the leaf 

 and tree — must have the same form. The form of the leaf will be to 

 some extent modified by the quantity of parenchyma, and the form 

 of the tree by the weight of the branches ; and there are other causes 

 producing a discrepancy. But the two — the leaf and tree — will com- 

 monly assume the same form. Even when they differ, the corre- 

 spondence will be seen in the tendency^ apart from extraneous causes, 

 to take the same form. It is always lo he remembered that it is the 

 whole leafage com'ivg out at a given place which represents the tree, 

 and the single leaf, where there are more leaves than one, represents 

 the branch or the young tree. It is only thus that I can bring the 

 ash and mountain-ash into accordance with these views. The whole 

 leafage, with its stalk, represents the tree, and the leaf-branch and 

 leaflet, the branches and branchlets, as also the young tree. 



" Such facts as these strongly incline us to the belief that in plants 



