July 6, 1888.] 



SCIENTIFIC NEWS. 



BUDS. 



A MONG the many pleasing and wonderful effects of 

 ■^^ Spring, there is none more striking than the rapid 

 expansion of buds into tender leaf. A few days of 

 warmth causes them to swell and burst so suddenly that 

 with many who have not thought about the matter their 

 formation seems to be a thing of the moment. But, as 

 will be presently shown, this is not so. Leaf and stem 

 were there in the previous autumn, and indeed in a 

 very rudimentary condition at an earlier period than that, 

 and very little has been added to the organ besides water. 

 In fact, buds may be made to develop into shoots with 



Fig. 1. Section of Leaf Bud of Euonymus. 



•a, b, axillary buds ; /, pith ; fv, fibro-vascular bundles ; c, 



cortex, i, 2, 3, young leaves. Magnified twenty times. 



only warmth, water, and oxygen for respiration, care being 

 taken in performing such an experiment to cut the branch 

 bearing the buds under water, to render it more absorbent. 

 It will contribute to a better comprehension of the matter 

 if we imagine that we have before us a " winter-bud " — 

 one from the spindle tree (Euonymus) will be a good 

 example — which we have dissected through the middle, 



from base to apex. We shall then see a central axis 

 tapering upwards from a thickish base to a fine point 

 and along its sides a number of leaves, so closely set as 

 to leave scarcely any interval, which tightly envelop the 

 axis and overlap its tip, to which they act as a protection, 

 but, it is important to note, do not, except in flower- 

 buds, grow from it. This central axis afterwards 

 becomes the stem, and the leaves which enwrap it will 

 be noted to consist of two kinds, the inner or foliage- 

 leaves, slightly succulent and light-green, the outer or 

 scale-leaves dryish brown and often sticky and hairy. These 

 latter usually fall away upon expansion, their function 

 being the protection of the inner and more delicate parts. 

 AH these characters are visible to the naked eye, but if 

 we now prepare a transparent nction showing the same 

 parts and place it under a low power of the microscope 

 (or, in the absence of such, a good hand-lens will be 

 helpful), we are able to make out the following important 

 additional details. Proceeding as before, from the centre 

 or axis, we observe first a lightish and, as a higher 

 power shows, a cellular portion, which is the pith in a 

 young condition, and this is bordered by two dark 



s ■ 



Fig. 2. The Growing Point of a Shoot (Winter Bud) 



of the Pine (after Sachs). 



S, apex of the growing point ; bb, very young rudimentary 



leaves ; rr, young cortex ; mm, pith of the future shoot axis. 



Highly magnified. 



columns of stringy tissue, which stop a little short of the 

 tip and give off branches to the leaves, in the younger of 

 which their presence becomes less evident. These columns 

 are the Fibro-vascular bundles {fv, fig. 1), and their func- 

 tion is the conveyance of gases and liquids through the 

 plant, and the maintenance of rigidity ; they spread out 

 into the leaves as the veins. External to these is another 

 lighter cellular region (c, fig. 1.), which is the bark in a 

 young condition, and from it the leaves arise. The leaves 

 (1, 2, 3, fig. 1) themselves are seen to be masses of cellular 

 tissue, interrupted by strands of vascular tissue, and be- 

 come smaller and less defined as they proceed towards the 

 apex until they dwindle down to little roundish promi- 

 nences on the upper part of the axis. But one of the most 

 striking circumstances in connection with them is the exist- 

 ence in a very rudimentary condition (being less evident 

 near the younger leaves) of next year's buds (a, b, fig. 1.), 

 in the axils or angles which the leaves form with the stem. 

 If we now raise the magnifying power to about 400 dia- 

 meters, the vascular nature of the darker tissue and the 

 cellular nature of the lighter will be rendered evident at 

 once, whilst at their terminations the character of that most 

 important part of the bud, the apex, or the growing point 

 (fig 2), also becomes more clearly defined. It is seen to con- 



