840 JOURNAL OP FORESTRY 



Each soil was placed in a wooden flat approximately 8 centimeters 

 deep, over which was placed a lath screen made so as to give half shade. 

 All flats were kept in the open, were given no artificial watering except 

 during the first two days to insure establishment of the plants, and were 

 all under the same conditions except for the soil. These conditions 

 were, furthermore, as close to natural forest conditions as possible. 



Measurements made at the end of the season of similar seedlings 

 growing in the place from which those for the experiment were taken 

 showed that the growth on all the flats was considerably less than that 

 in the forest, in spite of the heavier shade in the forest. This is prob- 

 ably due to two causes : first, the bottom of the flats prevented the ascent 

 of capillary water, rendering moisture conditions less favorable than in 

 the forest ; second, the disturbance of the roots caused by transplanting 

 would tend to make the growth of the transplants less than that of the 

 seedlings growing undisturbed in the forest. 



Soils 



The three soils were : 



(i) A thoroughly decomposed forest humus which had been taken 

 from the forest and rotted in a field for two years. 



(2) Undecomposed raw humus, taken directly from the spruce asso- 

 ciation, and consisting of needles, cone scales, and other forest litter. 

 This is Coville's "upland peat," the forest "dufif" which accumulates in 

 northern regions because decomposition is retarded by lack of sufficient 

 warmth. 



(3) Mineral soil from beneath the raw humus. This is a reddish 

 brown bouldery glacial till in which the rocks and boulders comprise 

 about 50 per cent or more of the volume. For the experiment only the 

 soil in between the rocks, from which all but scattering small pebbles 

 had been removed by hand, w^as used. 



Physical Properties of Soils 



Physical properties of soils are best given in terms of the physical 

 constant which bears the closest relation to plants. The wilting co- 

 efficient, though perhaps not strictly a physical constant," gives the best 

 idea of the physical properties. Unfortunately direct determinations 

 were impossible, except on the decomposed humus, because neither 

 wheat nor corn would produce sufficient root systems on these soils. 

 On the decomposed humus a single direct determination gave a wilting 



' Free, E. E. : "Studies in soil physics." Plant World, Vol. 14, pp. 29-39, 59-66, 

 110-119, 164-176, 186-190, 191 1. 



