154 TRANSACTION'S OF ROVAL SCOTTISH ARBORICULTURAL SOCIETY. 



of light necessary for its development. This optimum in some 

 species is almost identical with the total daylight, while in other 

 species it is less than the total daylight. ^ 



Conclusions, 



While the above experiments are admittedly of too specialised 

 a nature to warrant any generalisations from them, yet it will be 

 seen that, for the species oak and beech in the locality under 

 observation, light-intensity influences to a considerable extent 

 and in a very definite manner the distribution and development 

 of the advance growth. The conditions under which advance 

 growth occurs in a forest are very similar to those under which 

 natural regeneration is brought about, the main difference being 

 in the fact that groups of advance growth receive less side light 

 than natural growth which has resulted from the carrying out of 

 regeneration fellings. An attempt is made by means of the 

 above experiments to determine, more or less accurately, the 

 conditions most favourable to the development of advance 

 growth ; in other words, to determine approximately the optimum 

 conditions for natural regeneration. Long experience has shown 

 that for the oak the lightest possible shade of seed-bearers is 

 compatible with most successful natural regeneration. So, for 

 successful natural regeneration of the beech, experience teaches 

 that a considerable amount of shade is all-important. It is seen 

 from this, that the results of the above experiments are in close 

 agreement with the results of experience. 



This being so, the suggestion is offered that further experiment 

 may with advantage be undertaken for the same species in 

 different localities and also for other species in varying localities. 

 In this respect, certain Scots pine forests in Scotland appear to 

 offer good ground for experiment. For example, the district of 

 Strathspey contains perhaps the largest naturally regenerated 

 forests of Scots pine in Scotland, and parts of these are at present 

 in different stages of the process of regeneration. In addition, 

 there are on the outskirts of this district extensive areas of natural 

 Scots pine woodland, which afford many examples of advance 

 growth. Thus there are opportunities here for carrying out 

 parallel investigations on the advance growth and on the natural 



' See Lii^hl in Relalioii to Tree Grozu/h, Viy Raphael Zon and I fenry S. 

 Graves, U.S. Deparlnienl of Agriculture, P'orest Service — Bulletin 92. [This 

 pamphlet is noticed in this issue on pp. 181-202. — Hon. Eij,] 



