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plant, with its side leaves or branches. It may be observed, too, how, 

 in these plants last named, the lateral leaves and the lateral veins of 

 leaves both come off at a pretty wide angle. 



" In such plants as these it will be acknowledged, I think, that the 

 stems of the plant and the main veins of the leaf seem to follow the 

 same laws, or rather that it is impossible to distinguish between them 

 in some cases, and say what is the main vein and what is a stem. 

 But we may mount higher, and now examine our common trees, and 

 inquire if the veins of their leaves do not follow the same law of 

 direction as the lateral stems from the trunk and branches. No 

 doubt we may expect here to find, owing to the more complicated 

 structure of the plant, and its greater exposure to external influences, 

 that the phenomena will be more comphcated, and all that we can 

 expect to discover is a tendency on the part of the ramification of the 

 branches to take the same form as the venation of the leaves. Let us 

 take up a gooseberry leaf and examine it, and we shall find that at 

 the top of a leaf-stalk there go off three very large veins, with two 

 other lesser veins from each of the outer of the three large veins, 

 making in all seven veins from the base of the leaf; and we may no- 

 tice how the gooseberry, at the top of a short unbranched trunk, sends 

 off a large number of stems. We may now see, too, how the currant 

 leaf, at the top of a leaf-stalk, sends off from its base three main veins 

 (with other two less ones), and how, some little distance above the 

 ground, the trunk commonly divides into three main branches. 



" I have already traced some points of analogy between the ramifi- 

 cation of the branches and leaf-veins of our common trees. I have 

 examined the mountain-ash, and found that the angle of its leaf-vein 

 is 45°, and that the angle of ramification is also 45°. A dogberry 

 growing near was measured, and gave the angle, both of ramification 

 and venation, as 64°. Here, then, are two trees differing in their 

 angle by 20°, and in each case the angle of branch and vein corre- 

 sponding. But in carrying out the principle, it is to be borne in 

 mind that the full-grown tree is much more complicated than the 

 young tree or the simple branch. In such cases I apprehend that 

 the leaf represents exclusively the young tree or the branch. This is 

 the case with the laburnum, where the individual leaf represents the 

 branch, with veins going off at an angle of 60° or 70° ; but the 

 trefoil leaf will represent the whole tree, which tends to send off its 

 main branches in threes. 



" I think it proper to add, that while strongly convinced that there 

 is a truth in this doctrine, I am at the same time prepared to believe 



