144 LEAVES AND BUDS. 



Now look backwards along the twig, to find the place where last 

 year's end-bud was : how does this enable us to see exactly how much 

 the twig grew each year, at least for several years back ? Why is it 

 that a series of these "girdle-scars" or bud -scale -scars is always found 

 at the base of a side-twig, where it joins the parent-twig ? Does a 

 twig always grow equally long, or bear an equal number of foliage - 

 leaves, every year? In the case of a horizontal branch, which buds 

 grow into the most vigorous (as regards length of stem and number of 

 leaves) twigs the upper ones, the lower ones, or those on the flanks of 

 the branch? Why do you suppose the horizontal branches differ in 

 this respect from those which are erect or nearly so ? If you recall 

 your studies on the work of leaves, you will probably conclude that 

 light is the chief factor concerned, bit you should stop and think 

 the matter out. If you cut off a horizontal branch and set it erect in 

 water, how do the four rows of buds behave after opening ? 



At what time of year are the resting-buds formed ? Can you see any 

 trace of them, in the axils of the new leaves, just after the bud has 

 opened and the young shoot has grown out? Notice how the buds 

 grow in size during the summer. 



Is it possible to cause the young buds to grow out at once instead of 

 resting until next spring? Try the effect of pulling off the leaves from 

 a twig ; the buds may thus be caused to grow out a year before the 

 proper time. This precocious growth of buds is sometimes seen in the 

 Sycamore and several other trees, owing, in some cases at least, to 

 external causes (e.g. a late period of wet weather preceded by a dry 

 early summer and followed by a mild autumn, or the early dying of 

 leaves through dry cold spring winds, or attacks of insects), or simply 

 to excess of food; these "Lammas shoots" are often seen on Oaks, 

 Beeches, Horse Chestnuts, etc. In these cases leaves which had 

 arrested their growth in order to form bud-scales resume growth and 

 become foliage-leaves, bearing resting-buds in their axils. 



178. Horse Chestnut (see Art. 393). The arrangement 

 of leaves and buds on the stem, and the general structure of 

 the buds, are the same here as in the Sycamore. The twigs 

 (Fig. 50) are thick, smooth, grey or brown, with conspicuous 

 lenticels. The large leaf -scars vary from being shield- shaped 

 to half -moon- shaped, with scars of from five to nine bundles. 

 The uppermost bud is generally larger than the others and 

 contains a young inflorescence in addition to young leaves, 

 but the true end-bud is often missing and represented by the 

 saddle-like scar of the fallen inflorescence. 



The buds are egg-shaped, pointed, brown, shiny, arid sticky. Remove 

 the hard concave scales, which are more or less cemented together by 

 the sticky substance. Note the arrangement of the scales in pairs, set 

 at right angles to form four rows ; the two lowest (outermost) scales are 

 smaller than those of the next pair, and these are again smaller than 



