Germination of Forest Trees g 



The effect of light upon the height growth of forest trees has 

 been used as a basis for determining the relative tolerance of these 

 trees. As early as 1866 Kraft (2) planted a number of different 

 species in the shade of older trees and measured their heights and 

 diameters several years later. Upon this basis Kraft arranged 

 the species according to their tolerance. Nikolsky (2) in 1881 

 carried on similar experiments with pine and spruce and showed 

 that the greatest length of stem was found in the trees which 

 grew in the shade; the length of the entire plant above ground 

 increased with increase in shade ; the length of the main root as 

 well as the number and total length of the lateral roots, however, 

 diminished with increase in shade, while the total length of all 

 roots of plants which grew in great light intensity was greater 

 than the total length of all the roots in the shaded rows. At the 

 Swiss experiment station in 1893 Badoux (2) carried on experi- 

 ments on eleven tree species with different degrees of shading to 

 determine their behavior in different light intensities and thus 

 determine their tolerance. Fir and spruce had almost the same 

 average height growth at different degrees of shading. With 

 pines, larch, beech, and ash the growth on the contrary decreased 

 in proportion to the shading. In the case of basswood, blue 

 beech, and elm the growth in height was but little affected. The 

 work of Wiesner (2) from 1905 to 1909, in various parts of the 

 world, and of Clements and Pearson in the United States (2) 

 between 1907 and 1909 was only for the purpose of determining 

 the minimum light requirements of species as a basis for scales of 

 tolerance. The last two investigators took numerous readings 

 in the Rocky Mountains and noted the condition of seedlings 

 under various light intensities. 



Burns (9) experimenting with white pine under lath shade in 

 the nursery found that shading delayed the time of germination 

 but that the final germination per cent, was about the same in 

 both cases. He likewise raised white pine seedlings in full shade, 

 half shade, and no shade and (at an age which he does not state) 

 measured the length of the hypocotyls, tap roots and lateral root 

 branches. He found the greatest length of hypocotyl in the 

 plants that had been grown in the full shade, the greatest length 



