'physiologically considered. 529 



that for the formation of the woody fibres another power co- 

 operates, which, as proceeding from the bud representing, as it 

 were, a perfect individual, we may compare to the formation of 

 roots. It would hence appear that the wood of the graft never 

 passes over into the stock, as it must always assume the nature 

 of the surrounding bark from which the creative sap is trans- 

 mitted; and that the spiral vessels may be jointed, and the cells 

 of the fibres between the knots closed, as the creative sap always 

 strives to assume the cellular form, while the peculiar active 

 power of the bud stretches them to long fibres of various ana- 

 tomical forms. The property of forming roots is not, however, 

 peculiar to buds, but also to many persistent and succulent leaves ; 

 but here there is often a very striking difference. For while, 

 with few exceptions, the roots of the cutting proceed, not from 

 the surface of the cut, but from the sides at the base of the knot 

 under the bud, and are therefore to be considered as proceeding 

 from it, the roots of leaves taken off without any axillary buds 

 come chiefly from the surface of the cut, and sometimes also 

 from the side of it. In some of the gesnerias they spring from 

 the outside of the circular bundle of woody fibre of the leaf- 

 stalk, and may be very clearly distinguished for some depth in 

 the leaf-stalk, and have their origin, as it appears to me, in 

 a new layer of wood that was forming near the old one. Side 

 roots, also, were produced from this ring. 



Accoi'ding to their different situations, we distinguish top or ter- 

 minal buds, axillary buds, and the scattered or adventitious buds 

 which may spring from almost all parts of the plant. These are 

 produced in great numbers on many plants by cutting in the old 

 wood, and they also sometimes appear on the roots and leaf- 

 stalks or petioles of dicotyledons. All buds have an axillary form, 

 which is enveloped in a number of overlapping leafy growths or 

 scales ; and, as the continuation of the axis of the parent plant con- 

 sists of pith, or medulla, and medullary envelope (Mai'kscheide) 

 if the bud is growing on a young branch, the pith passes over 

 into it directly; but if the bud proceeds from old wood, the pith 

 is connected with the medullary rays; the passage of the bundle 

 of spiral vessels which form the medullary envelope being 

 tolerably clearly distinguishable. The latter becomes some- 

 what broader before it ends below the top of the bud, and from 

 it is afterwards formed the inner layer of wood. Over the 

 enlarged end of the medullary envelope, the pith rises convex 

 or conically, forming the medullary point (Markhiigel). On 

 the outside it is surrounded with a fine brownish network of 

 cellular tissue, which afterwards forms the bark, and passes 

 directly into the outer cells of the bud leaves. At the base of 

 each of these leaves there is the beginning of a new bud, which 

 is never developed as a normal bud. On the upper extremity 



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