106 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



modifications of structure that are favourable under such cir- 

 cumstances prove very disadvantageous in a dry chmate, where 

 the tendency for rapid diffusion of the moist gases in the tissues 

 I of the tree with the outside air must be checked by a thick 

 cuticle and by small stomata. Trees, therefore, that are raised in 

 a dry climate from seed gathered in a humid region are, in their 

 early stages, very apt to suffer excessively from drought, and 

 may die altogether, although, should they survive the period of 

 youth, they may become acclimatised and adapted to their new 

 conditions. 



Many practical foresters lay considerable stress on the careful 

 selection of the best-formed trees from which to save seed, and 

 this appears to be at least a safe course to pursue. It is true 

 that some entirely deny that the seeds of trees stunted by high 

 elevation or poor soil produce seeds of like character. Others, 

 again, point out that, even granted that they do, such trees will 

 be overgrown very early in the life of a wood by the more 

 vigorous trees, and as they are removed in the thinnings they do 

 not affect the main yield. This is, of course, assuming that all 

 the young trees made use of in forming a wood have not been 

 raised from the seed of stunted trees, but that such seed has 

 been mixed with other seed yielded by large and well- developed 

 trees. In a plantation, and still more in a natural forest, the 

 struggle for existence and the survival of the fittest can be very 

 advantageously studied. Those trees which, owing to inherent 

 qualities or injuries, or the accident of position, display lack of 

 vigour in early youth are immediately overgrown by their 

 more robust neighbours, and cease to take any further part in 

 the history of the wood. The result is the same whether man 

 interferes or not. If it is a virgin forest these weaklings simply 

 die, decay, and disappear ; while, if the wood is under artificial 

 management, they are removed in the thinnings. During the 

 whole existence of the wood there is a constant shedding- out 

 process at work, the weakest individuals succumbing and the 

 strongest surviving ; so that at the end of a hundred years or so 

 — and in the absence of abnormal disturbing causes, such as 

 wind — the two hundred trees or so that occupy an acre repre- 

 sent those of the original number that were best fitted for the 

 circumstances under which they were placed. In nature it is 

 chiefly those trees that shed the seed from which the succeeding 



