Germination of Forest Trees 9 
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 
