134 EXPERIMENT STATION RECORD. [Vol. 41 



The index of transpiring power of plants, E. B. Shke\'e (Carnegie Inst. 

 Washington Year Book, 17 (1918), pp. 72-74).— Having noted previously (E. S. 

 R., 40, p. 27) a large opening for error in the assumption that the tripartite 

 cobalt paper slips for determining index of transpiring power are at the same 

 temperatui-e as the surrounding air, the author has employed an adaptation of 

 the thermocouple referred to below to test the temperature of the cobalt paper 

 slip as it rests upon the leaf under its grass cover. This work has established 

 the fact that the temperature of the air may be safely taken as the temperature 

 of the cobalt slip. It is also shown that if cobalt slips are standardized at 

 within 2 or 3° of 20° C, the error introduced is smaller than that obtained from 

 consecutive readings on the same slip at any given temperature. 



Modification of root habits by experimental means, W. A. Cannon (Car- 

 negie Inst. Washington Tear Book, 11 (1918), pp. 83-85). — These observations 

 appear to show that roots which penetrate deeply, or which ordinarily grow 

 in soils of fine texture, are less responsive to relatively small changes in soil 

 aeration and may be less dependent on temperature than is the case with roots 

 which are essentially superficial and which occur only in relatively well-drained 

 soils. Exceptions are noted. Cultural experiments with species whose roots 

 remain close to the surface and which have well-fixed characters show a sur- 

 prising plasticity in root development. It is claimed that in certain cacti the 

 distinctive root characters do not result from inherited tendencies, but are 

 probably expressions of the response of the species to the distinctive aeration 

 and temperature conditions of the soil environment. 



"Water content and abscission in the nuts of Juglans califomica quercina, 

 F. E. Lloyd (Carnegie Inst. Washington Year Book, 17 (1918), p. 76). — A record 

 having been kept on numerous fruits of J. califomiea quercina of such as ulti- 

 mately became separated from the twig by abscission, it is stated that a daily 

 net gain was made which decreased until an uncompensated loss occurred. In- 

 adequate water supply is thought to be the exciting cause of abscission, which 

 closely i-esembles that occurring in the cotton plant (Gossypium). 



Calcium oxalate in the dasheen, O. P. Black (Amer. Jour. Bat, 5 (1918), 

 2\o. 9, pp. 447-451). — Investigation of tubers and leaves of the dasheen is con- 

 sidered to show that the calcium oxalate crystals are the sole cause of the acrid 

 taste, which is supposed to be due directly to mechanical irritation by the 

 needles coming in contact with the mucous membrane of the mouth. It is 

 stated that proper cooking will remove the crystals and render the plant use- 

 ful as a vegetable. 



Sterility and self and cross incompatibility in shepherd's purse, G. H. 

 Shuul (Abs. in Science, n. ser., 49 (1919), No. 1275, p. 547). — An abstract is 

 given of a paper read before the American Philosophical Society in which the 

 author describes the result of crossing the common shepherd's purse of the east- 

 ern United States with a form that occurs on the Pacific coast. The form from 

 eastern America is characterized by sterility of the lower flowers of the main 

 axis, while the western species does not show this condition. As a result of 

 study of the crosses made, there was found to be a rhythmatic succession of ster- 

 ile and fertile flowers, and there seemed to be some evidence that this ar- 

 rangement was xnider the control of two genetic factors. 



Culture of a potato hybrid, Solanum fendleriXS. tuberosum (" Salinas"), 

 D. T. MacDougal (Carnegie Inst. Washington Year Book, 17 (1918), pp. 87, 

 88). — Cultures of the hybrid between the wild potato of Arizona and the do- 

 mestic variety have been carried on at the Coastal Laboratory and on a ranch in 

 the Carmel River Valley, resulting in the separation of a number of elements of 

 different value. Studies are being made on about a dozen strains of possible 

 economic importance. 



