116 PLANT LIFE ON THE FARM. 
comparatively poor soil which would starve other plants 
with less capacity for food collection and less duration of 
working life. The larger the leaf-surface, and the more 
fully and thoroughly it can be exposed to light, the 
greater quantity of timber and the sounder its quality. 
It may be requisite for certain purposes to have straight 
unbranched spars, and, in such cases, leaf-action is im- 
peded and side-growth is arrested by thick plantations 
and neglect of thinning ; but the actual amount of tim- 
ber is necessarily less in such trees than in others of the 
same age allowed to develope freely on allsides. Coppice 
wood is also grown for a special purpose, which practically 
justifies that mutilation which, like most pruning opera- 
tions, is of course at variance with natural growth. In 
the annual growth of timber it may readily be seen that 
the ‘greatest activity of growth, t.e., formation of new 
tissues, takes place in the first few weeks after vegetation 
commences. After that, the period of maturation or 
consolidation commences. A moist, warm, growing 
period is, therefore, most propitious. The process of 
maturation requires for its fulfilment greater heat, less 
moisture, and more intense light, and in proportion to 
the degree in which these requirements are satisfied, are 
the amount and quality of the timber. Should a wet, 
sunless autumngbe succeeded by an early frost, when 
maturation is imperfect or incomplete, the results to the 
young growth, that is, to the crop of timber for the year, 
are correspondingly disastrous. The effect of mineral 
manures, especially potash, in promoting the develop- 
ment of the fibrous tissue in grasses, has been already 
alluded to; the largest absolute amount of straw being 
yielded by a mixed mineral manure with a large supply 
of ammonia. 
Plants grown for their seed.—The remarks just made 
as to the development of timber as a consequence of 
