ABSTRACT OF RESEARCHES ON THE ANATOMY OF BUD-SCALES. 275 



most part, on the upper side, corresponding to the inner in tlie bud- 

 scale. 



A peculiarity, which has nothint^ corresponding to it in leaves properly 

 so called, is the anatomical ditierence which exists most frequently 

 between the inferior and protected part of the bud-scales and their upper 

 and naked portion. The external scales being wholly naked, it is only 

 at their lowest portion, where they are attached to the stem of the bud, 

 that they present any difference from the upper portion ; in all the other 

 scales this distinction exhibits itself throughout the whole p7-otec(ed portion. 

 Speaking generally, the cellular tissues of these portions resemble those 

 which compose tiie stem in its earliest state in the bud; they are more 

 tender, and have their walls thinner than in the upper portion. Even when 

 the internal structure of the bud-scales is only composed of a kind of 

 liber, with vascular bundles, as in the Beech, this holds true, at least as 

 to the delicacy and thinness of the cell-walls. In other respects, the 

 differences may involve either the colour of the cell walls, and even the cell 

 contents, or the structure of the cellular tissues. In these two cases the 

 modifications go on augmenting from the base of the bud-scale to the 

 apex, and they are more manifest on the outer side than on the inner. 

 The difference of colour depends ordinarily on the changes which the cell 

 contents undergo : the lower part of the scale contains cells with colour- 

 less cell walls, and cell conteiits fre(|ueiitly containing chlorophyll, but 

 often colourless and muddy-looking ; but in the upper part these are 

 transformed into a sap often brilliantly coloured (Tilia, Salix), or into a 

 brown and resinous substance, which infiltrates and tinges the cell-walls 

 either of the epidermis alone or of the rest of the cellular tissue as well 

 {^Rhamnus alj/iud, L.). 



In so far as the difference between the upper and lower part of the 

 scales depends on the cellular tissues, the former may consist of cork or 

 bast fibres, while the latter resembles more the stem within the bud. 

 However, the different structure of the bud-scales at different heights 

 does not always correspond to the cellular tissues of the stem and that of 

 the lower part of the scale; frequently the cellular tissue of this,. as, for 

 example, in many conifers, consists of a layer of cork (^Abies excelsa, 

 De Cand.), or is even transformed, for the most part, into a viscous 

 matter {Ulmus inoitana, Sm ). On the other hand, there are bud-scales 

 {Msculiis, Fraxinns) where there is no noticeable difference betv een the 

 two portions, and this is especially the case with those in which the 

 cellular tissue contains chlorophyll, and the function of warmlh-retaining 

 seems to belong to the epidermis. 



The variety in the iiuier structure of the bud-scales depends upon the 

 fact that it is sometimes one, and sometimes another, of the cellular 

 tissues of the stem which forms the principal portion. 



It is only the tissues, however, existing outside the cambium of the 

 stem which contribute, in a considerable extent, to the formation of buil- 

 scales ; the cambium and the vascular bundles, although they are never 

 wholly deficient, are always little developed. In fixing our attention on 

 the exterior bud-scales, and on the upper and naked portions of' the 

 iimer bud-scales, we shall find that their principal portion may consist of 

 the following cellular tissues : — 



1. Bud. — It is only the bud-sealcs of Fagus si/Ivalica, L., that consist 

 wholly of bast ; in other cases bast bundles arc found, in addition to 



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