90 THE DEVELOPMENT OF BRITISH FORESTRY 



for those months. He believes that the growth of most 

 timber trees can be completed within six weeks under the 

 most favourable conditions, but that no data are available 

 to show what these conditions are, nor how far intensive 

 light can replace heat in the process of growth. 



So far as Britain is concerned, however, it is practically 

 certain that the conditions are rarely favourable enough 

 for growth to take place within such a short period. The 

 actual time occupied in the increase of length of shoots 

 of certain species is very short, but the maturing of wood 

 and buds occupies a longer period, which is difficult to 

 fix with any certainty. Oak, beech, pines, etc., seldom 

 increase in length for more than three or four weeks in the 

 latter part of May or beginning of June, and with the two 

 first named this growth is often repeated in July in the 

 form of midsummer shoots. Assimilation and the process 

 of forming and ripening the wood go on until the end 

 of August or possibly September, but visible growth in 

 most species is much shorter than is generally supposed. 

 Four months is more than sufficient for the growth and 

 maturing processes of most species, and the actual time 

 occupied in the formation of an annual shoot is rarely 

 more than six to eight weeks. Exceptions to this are 

 possibly larch, elm, hornbeam, willow, poplar, and 

 alder, all of which grow so long as the temperature 

 remains high enough. With these it is doubtful, how- 

 ever, if the growth made during the first and last month 

 of the growing season is sufficient to make any appreci- 

 able difference, except to young plants which respond 

 more readily to climatic conditions than older trees. 

 Favourable conditions of temperature and moisture pre- 

 vailing over a period of three months are probably 

 sufficient to produce and mature a normal growth in all 

 conifers, and the majority of broad-leaved trees. 



The ripening of the seed depends more upon the length 



