160 BOTANICAL GAZETTE [FEBRUARY 
toxic aluminum salts may never be found, but in soils deficient in calcium and 
other bases, as in acid soils, toxic aluminum salts are largely the end products 
of sulphofication and nitrification. It is not denied that iron and manganese 
may become contributing factors in the unproductivity of some acid soils, 
but the preponderance of evidence points to aluminum as the determining 
factor in the acidity of the soils under investigation.” —Wwa. CROCKER 
Soluble substances in soils—McCoor and Mrrrar’ have studied the 
rate at which substances become soluble in soils of various origins, types, ages, 
etc. The solubility was determined by the Bouyoucos freezing point method. 
The soils were leached free from soluble materials and then allowed to stand 
in water for various periods (5, 10, 30, and 60 days), and the freezing points 
determined at the ends of these periods. Contrary to the common view, soils 
from regions of lower precipitations are not more soluble than those from 
higher precipitations. The so-called new soils are less active than those some- 
what older, and aged soils are almost inert. Subsoils liberate soluble salts 
very slowly, there being little activity below 6 inches. Sand particles are very 
rin t n 
per then washed free of soluble materials, the rate of dissolving was siligtirhle 
ted. estern soils responded somewhat more readily than others. 
Michigan Agricultural Experiment Station is studying this problem from 
several angles (composition of the soil, solutions on cropped and uncropped 
soils, residuary effects of salts on soils of different texture) and the work 
promises to be a valuable contribution to our knowledge of soil fertility. 
—Wwm. CROCKER. 
ee | in lohets -—COVILLE? has emphasized the significance of cold in 
dormancy. He finds temperatures of 32-40° F. 
the most effective, and emphasizes the transformation of starches to sugars as - 
an important result of the low temperature. The effective temperatures 
agree well with those found for eg after-ripening of dormant embryos in this 
laboratory.— WM. CROCKER. 
Living stumps.—The continued growth of stumps and the healing over 
of the cut surface is not uncommon in the case of Pseudotsuga. PEMBERTON,” 
investigating the phenomenon on Vancouver Island, British Columbia, finds 
the continued growth of the stumps due to the transference of food from living 
trees connected with stumps by means of subterranean root grafts. Instances 
are cited when growth ceased immediately with the cutting of the host 
ee.—GEO. D. FULLER. 
8 McCoo1, M. M., and MILLAR, C. E., The formation of soluble substances in 
soils taken rae widely separated regions. Soil Science 10:219-235. 1920. 
9 CovILte, F. V., The influence of cold in stimulating the growth of plants. Nat. 
Acad. Sci. eschew 1920. 
10 — C. C., Living stumps of trees. Amer. Forestry 26:614-616. 
figs. 6. 
