116 PLANT LIFE 0$ 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 -surf ace, 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 all sides. 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, i.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 autumn be 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 



