CURRENT LITERATURE 



Studies in Tolerance of New England Forest Trees. III. Dis- 

 continuous Light in Forests. By G. P. Burns. Bvilletin 193, Uni- 

 versity of Vermont and State Agricultural College. Burlington, 

 Vt. 1915. Pp. 23. 



This interesting bulletin exhibits the hopelessness of the at- 

 tempts to investigate the scientific basis of tolerance and in- 

 tolerance by the methods hitherto piu-sued, namely of measuring 

 the light intensities in the forest with its discontinuous shade 

 and bringing them into relation with seedling development, and it 

 describes a new departure in method, namely by growing seedlings 

 under a devised habitat with continuous shade. 



Like many inventions, the idea is not entirely new, for many 

 years ago Borggreve in the garden of the Academy at Miinden in- 

 stituted such experiment, to disprove his predecessor, Heyer's 

 philosopy of tolerance, albeit in a much cruder and unscientific 

 form. 



At the outset we must take issue with the author's statement 

 in the introduction, repeated in the conclusion, that "the word 

 'tolerance* should be stricken from the vocabulary of forestry 

 students imless to it can be accorded a more comprehensive defini- 

 tion. It is taken generally to express a light relationship, but 

 really it expresses not a light relationship, but the total relation- 

 ship of a tree to all factors of the habitat." Nor is it true that 

 "if the trees are developing slowly, they are 'intolerant;' if they 

 are developing rapidly, they are 'tolerant.' " 



If the reviewer may presume to speak for the profession, fores- 

 ters mean only a Ught relationship and nothing more when they 

 speak of intolerant or Hght-needing species and tolerant or shade- 

 enduring species, expressing thereby dijQEerences in the amount or 

 intensity of light required for satisfactory development. That 

 the development, and even the light requirement itself, is influenced 

 by other factors of the habitat or site is perfectly recognized and 

 does not by any means exclude the influence of light tmtil this is 

 disproved. 



Nor is the slow or rapid development (of the seedling?) the only 

 criterion by which the forester recognizes relative light require- 

 ments. The character of the foliage, the inability of foliage 



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