II AMENTACE.^ 363 



The explanation which I have suggested is as follows : 

 — The leaves of the evergreen Oak are entire, and 

 small in comparison with those of the English Oak. 

 During the winter and early spring they are protected 

 -by a series of brown scales, inside which they lie, form- 

 ing the familiar buds, which are both small and short 

 in proportion to the size of the leaves themselves. 

 In cooler and moister regions, on the contrary, there 

 is, as we know, a tendency for leaves to become 

 larger and deciduous. These influences do not, how- 

 ever, affect the outer scales, which remain as before, 

 without any increase of size. But as the leaves have 

 increased in size and the buds 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 (Fig. 271) is, on the contrary, 

 shorter than that of the Beech (Fig. 253). Under 

 tliese 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, however, there would be 

 no room within the narrow limits of a bud, or rather, 

 perhaps, they would be inconvenient because they 

 would leave more or less empty spaces. This may be 

 rendered more clear by taking a piece of cloth or paper, 

 folding it up, and then throwing it into a curve. It 

 will then necessarily fall into one or more folds. If it 

 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 characteristic of the Oak leaf These sinuses are due, 



