126 LINNEAN SOCIETY OF LONDON. 



lie, and with which they form the well-known buds so familiar to 

 us, and which are both small and short in proportion to the size of 

 the leaves themselves. In cooler and moister regions, on the con- 

 trary, there is, as we know, a tendency for leaves to become larger 

 and deciduous. These influences do not, however, affect the outer 

 scales, which remain as before, without any increase of size. But 

 as the leaves have increased in size, and the scales have not, the 

 leaves can no longer retain their original arrangement in the bud. 

 If, for instance, we compare the buds of the Oak and of the Beech, 

 we see that while the leaf of the Oak is longer than that of the 

 Beech, the bud of the Oak is, on the contrary, shorter than that of 

 the Beech. Under these circumstances, what must happen ? The 

 leaf grows, and becomes longer than the bud. It is, therefore, 

 necessarily bent into a curve. But an entire leaf, if thus thrown 

 into a curve, would necessarily fall into folds, the number being 

 determined by the number of ribs or veins. For such folds, how- 

 ever, there would be no room within the narrow limits of a bud, or 

 rather, perhaps, they would be inconvenient, because they leave 

 more or less empty spaces. This may be rendered more clear by 

 taking a piece of cloth or of paper, folding it up, and then throwing 

 it into a curve. It will then necessarily fall into one or more folds. 

 In the membrane it is flat when the midrib is bent ; then, when 

 the midrib is extended, intervals must occur. If the membrane 

 were strengthened, as an Oak-leaf is, by three or four side-ribs, 

 there would be a fold between each two ribs. As a matter of fact, 

 however, from the absence of space the membrane where the fold 

 would be is not actually developed. We may imitate this by 

 removing them. If this be done, the result will be the formation 

 of sinuses rounded at the base, closely resembling those so charac- 

 teristic of the Oak-leaf. These sinuses are due, then, as I believe, 

 to the curvature of the leaf, owing to the shortness of the bud in 

 comparison with the length of the leaf open out. Moreover, the 

 young leaf is not only curved, it is wrapped round the interior leaves. 

 The result of this is that one side of the leaf is folded withm the 

 other ; the one, therefore, being on the outer side, has more space 

 than the other. The two sides of the leaf are in fact differently 

 situated, and this, I believe, accounts for the second point — namely, 

 the want of symmetry. The oblong form is an advantage, from the 

 way the leaves diverge from the stalk. In this manner the 

 interesting peculiarities of the Oak-leaf may be accounted for. 



(3.) "On the Leaves of Viburnum." We have in this country 

 two species of Guelder Bose — Viburnum. They are nearly allied, 

 but the leaves are very dissimilar, those of V. Lantana being oval or 

 ovate, and, when young, very hairy ; those of V. Opulus three-lobed, 

 smooth, and provided with stipuliform appendages. These diffe- 

 rences are very interesting, but no one has ever attempted to explain 

 them. The young leaves of V. Lantana are sufficiently protected by 

 their hairy covering, and are consequently left bare. This is not the 

 case with V. Opulus, in which the leaves are glabrous. The outer 

 leaves, however, become tough and leathery, and form a covering 

 within which the other or true leaves are developed. To economise 



