1915] CURRENT LITERATURE 423 
he says, “Ricc has . .. . pointed out the seemingly peculiar distribution of 
Pseudotsuga taxifolia as limited to the north-facing slopes of the hills.” It is 
perhaps generalizing too much to say that the species under discussion is con- 
fined to the north-facing slopes “‘in a// more or less arid regions,” although the 
phenomenon is undoubtedly of frequent occurrence. If the reviewer inter- 
prets Cowles correctly, the absolutely rigid application of the principle quoted 
from his paper of 1901 is not in accord with the spirit of his more recent teach- 
ing. In regard to the quotation from the reviewer’s paper, the facts are that 
the paper cited pointed out four cases only in these islands where the forest is 
largely limited to the north-facing slopes. It would be generalizing too much 
to say that this is true in all cases in the islands. The whole subject of forest 
distribution in the San Juan Islands should be made the subject of a careful 
field investigation. The point of view from which the paper is written is very 
Suggestive and it forms a valuable contribution to the subject of forest dis- 
tribution in the Northwest.—Grorce B. Ricc 
Available soil moisture.—ALWAY” has grown plants in water tight cylinders 
until they die from lack of available moisture, and made careful determinations 
of the moisture conditions of the soils. He concludes that for comparing the 
available moisture in soils either the wilting coefficient or the hygroscopic 
coefficient may be used with equal efficiency. The former seems to him prefer- 
able in considering conditions of germination and growth of crop plants, and the 
latter in considering the seed production of such annual plants as field grains 
and the maintenance of life of perennial plants. Under the conditions of his 
experiments, most plants seemed capable of producing little or no growth after 
the soil moisture fell below the wilting coefficient, but whenever there was a well 
developed root system and no remarkably unfavorable conditions obtained, 
the plants were able to reduce the moisture content of the soil almost or quite 
to the hygroscopic coefficient, that is, to 68 per cent of the wilting coefficient. 
Little difference was found between the ability of the various crop plants used 
in the experiment to exhaust the soil moisture; while, on the contrary, marked 
n. 
The bulletin reports a good example of an investigation in a quantitative 
Manner of problems in La production important alike to agriculture and 
ecology.—Gero. D. Fut 
* Atway, F. J., Studies on the relation of the non-available water of the soil to 
the hygroscopic coefficient. Agric. Exp. Sta. Neb. Research Bull. 3:133. figs. 37- 1913- 
