302 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



THE AWAKENING OF BUDS 

 AND THE SLEEPING OF LEAVES. 



By Eev. Prof. G. Henslow, M.A., V.M.H., &c. 



Lecture to the Students at the Society's Gardens, June 18, 190L 



Intboduction. — Buds are primarily the result of the lowering of ten2- 

 perature in autumn ; for as soon as this rises above a certain degree they 

 burst open and begin to grow. But the elements of a bud are not merely 

 or entirely arrested structures, whether temporarily or not, as are the^ 

 minute leaves within them ; for the outer " bud-scales " are special 

 formations protecting the more delicate parts within. Now these scales- 

 are not always the same thing, for Nature is never at a loss to make any 

 structure, and if it be not convenient to construct it out of one thing she 

 simply utilises another for the same purpose, as we shall see. 



Bud-scales may protect the undeveloped leaves or flowers. I an) here 

 only concerned with the former. To find out what a leaf-bud consists*, 

 of we must collect some examples, and I would suggest the following as- 

 illustrating the remarks I am about to make. Horse-chestnut, Ash, ancl 

 Walnut, these have one kind of bud-scale ; Elm, Lime, and Hazel will be- 

 good examples of a second kind ; the common Laurel and Rose represent 

 a third sort ; while Lilac, Privet, and the W^ayfaring-tree {Vilmrnum 

 Lantana) will stand for a fourth. 



Of course there are many other kinds of buds, as those boine under- 

 ground by subterranean stems of various sorts, such as bulbils, corms^, 

 &c. ; but space will not allow for any further reference to these. My 

 object is to call attention to the peculiarities of buds of trees and shrubs., 

 hoping it may lead others to observe some very curious phenomena con- 

 nected with them for themselves. 



Petiolar Bud-scales. — Selecting a lateral bud of the Horse-chestnut., 

 it will be seen to have overlapping, dark browm, veiy sticky scales ;: 

 removing these there will be found a little woolly body in the middle, 

 and on " teazing " it out with needles it will be seen to consist of minute 

 leaves densely clothed in white wool, an excellent protection against injury 

 by low temperature, as wool is a non-conductor ; so that if one be spread 

 out flat it looks like a miniature woolly glove. Now, what are the leaf- 

 scales ? Let us imagine spring has come — and the bud must be examinee! 

 when it does — we shall find that the outermost dark brown resinous 

 scales are being thrown oft' (the sticky matter was secreted by their 

 surfaces), having now done their duty of protecting the leaves within ; 

 but the innermost and greener scales become more elongated and show 

 little stunted rudiments of blades at their tips. These reveal the fact 

 that the bud- scales are arrested leaves," but of which the petioles are 

 abnormally flattened, the blades remaining very minute. 



As soon as' the true leaves can escape, the observer must notice how 

 the leaflets at once curve downwards, so as to put their upper surfaces 

 in a vertical plane, for this position lessens the chance of injury from 



