FORMATION OF THE WINTER LEAF BUD. 



299 



leaves are very young, they are pressed together, their backs 

 exposed to the heat; probably to dry them, and clear the 

 pores for the reception of the carbonic gas; and as young 

 leaves give out hardly any oxigen, the shade in which the 

 other side is immersed is of little consequence. 



To prove, that in formingtheleaf I have given it no features, D . . - 

 but what it really possesses, I shall finish by showing all the the leaf, 

 parts of a full grown leaf. The colour of leaves is not to be 

 found in their substance, but in the liquid with which it is 

 filled. The darkest green leaf that can be taken, has a per- 

 fect white cuticle, both above and below it. In this cuticle 

 are the pores. It is rather a thicker net below than above; 

 but not enough to account for the difference of the tints; 

 but the under one lies not near so close to the pabulum of 

 the leaf as the upper one; which may account for the co- 

 lour not piercing so much through. When these two nets 

 are taken off, the pabulum of rhe leaf appears. It is form- 

 ed of little bladders, rilled with a dark green. liquid, and in- 

 terlaced with vessels. Take this off, and a bed of larger 

 vessels presents itself; then a collection of bladders, 

 which is followed by the larger lines of the leaf; and then 

 a bed of bladders repeated, which the under cuticle covers. 

 Though the bladders differ in size and colour in different 

 leaves, and in thickness also, yet the general arrangement is 

 the same. I mean not however to include either the Jirs, 

 the grasses, or those grassy leaves of early spring, the iris, 

 crocus, snowdrop, &c, which are all of a different nature, 

 as I shall show hereafter. 



I cannot quit the subject without adverting to the differ- Different sorts 

 ent sor.s of hairs, that are found on the back and face of the 

 leaf. 1 have before mentioned some on the former part, in- 

 tended to preserve the dryness; but on the face of the leaf 

 there appear often many tilled with moisture, as a kind ©f 

 reservoir for the cuticle, and these ar.e replete or not, ac- 

 cording to the dryness of the atmosphere. 



There is also an innumerable multitude of things, that Microscopic 

 are truly parasite plants, that grow on leaves, forming groves parasitical 

 and orchards for the various tribes of insects, that live and ^ a " * 

 bretd under them. As I do not wish to mix the different sub- 

 jects, I shall conclude this letter, but mean to trouble you 



with 



