THE SELF.CTJON SYSTEM 63 



erly located, so that some provision for seed distribution 

 must be made from among the old timber. 



Then, again, in mixed forests the intermediate trees 

 near an opening may not be of the species most desired. 

 The forester must endeavor to secure a distribution of 

 seed by leaving seed-trees properly located. In leaving 

 a seed-tree above the diameter limit, one must bear in 

 mind that it involves an actual investment, for the tree 

 might otherwise be taken out and sold. If the tree is 

 salable now, but will not be so at the next cut, one in- 

 vests its value in reproduction. If it is sound now, and 

 likely to remain so till the next cut, it is merely a ques- 

 tion of deferred profits. In anv case, one must be cer- 

 tain that a special seed-tree is required, and that it will 

 answer the purpose for which it is left. 



Successful reproduction depends not only on a prop- 

 er distribution of seed, but also on the conditions for 

 germination, and for the development of seedlings. The 

 problem is very simple with tolerant 1 species, for these 

 are able to grow in very small openings, and often a good 

 reproduction is already established where the openings are 

 to be made. With intolerant species, on the other hand, 

 special measures often have to be taken if they are to be 

 reproduced successfully. If such measures are not taken, 

 other more tolerant species may occupy the opening to 

 their exclusion. The opening must be large enough not 

 only to give the trees a start, but also to allow them to 

 make straight and thrifty growth. It is, therefore, some- 



1 Tolerant species are those capable of enduring more or less neavy shade 



