152 BOTANICAL GAZETTE [AUGUST 
same size and age, and were taken from the same place, so that 
variations due to size and vigor are eliminated. Each soil was 
placed in a flat approximately 8 cm. in depth, over which was placed 
a lath screen made so as to give half shade. All flats were in the 
open, were given no artificial watering after the first 2 days, and 
consequently were all under the same conditions except for the 
soil. These conditions were, furthermore, as close to natural forest 
conditions as possible. 
The 3 soils were (1) A thoroughly decomposed ‘forest humus 
which had been taken from the forest and rotted in a field for 2 
years. This has a moisture-holding capacity, when saturated, of 
138. 5 per cent of its air-dry weight, or 82.6 per cent of its volume. 
(2) Undecomposed raw humus, taken directly from the spruce 
association, consisting of needles, cone scales, and other forest 
litter. This is Cov1tLe’s “upland peat,” the forest “duff”? which 
accumulates in northern regions because decomposition is retarded 
by lack of sufficient warmth. Its moisture-holding capacity, 
saturated, is 504.6 per cent of its air-dry weight, but only 65.1 per 
cent of its'volume. The high percentage of water on the basis of 
air-dry weight gives an idea of the extreme lightness of this raw 
humus. (3) Mineral soil from beneath the raw humus. This is a 
___ bouldery glacial till, a reddish brown sandy loam with but little 
i properties 
faa The reason is that it was 
_ impossible to make wheat or corn produce sufficient root systems ce 
oS in either the raw humus or the mineral soil. On the decomposed - 
nus (soil [2] above) a single direct det wilting : 
effi aha of 13 per cent. Calculations from the  moisture-holding & < 
ci ty at B eeteree,. which : are probably unreliable for these” 
iIting nts of 21 sae 
