334 EXPEBIMENT STATION EECOED. 



centration of 1.75 atmospheres, which Is said to be a suitable strength for general 

 water-culture work. 



The absorption of ions by living and dead roots, H. V. Johnson {Amer. 

 Jour. Bot.. 2 (1915), No. 5, pp. 250-254) .—The author holds that unequal ab- 

 sorption of anions and cations by roots may be due to the dead rather than to 

 the living cells. In experiments with beets and carrots he found that the ratios 

 of the cations absorbed were different in the dead from those observed in the 

 case of the living plants. In sweet corn the dead roots took up somewhat more 

 calcium than chlorin, but this was not true of white field corn, which gave 

 results comparable to those of a single experiment made with dead turnips. 



It appears, therefore, that the presence of dead cells has a very marked in- 

 fluence on the results in some cases. It is suggested also that observed re- 

 sults may be vitiated by the killing of some of the cells by the solutions during 

 the exijeriment. 



The influence of Rontgen rays on the seeds of Vicia faba as shown in the 

 development of the plants, T. Pfeiffek and W. Simmermacheb {Landtc. Vers. 

 Stat., 86 (1915), No. i-«, pp. 55-45).— The authors have studied the after- 

 effects of Rontgen rays on V. faba seeds and seedlings, employing complete 

 darkness, the light from a north window, or that in the open. The seeds, before 

 being sprouted, were exposed to the rays for 30. 60, 90, 120, and 150 seconds, the 

 exact strenijtli of the tubes not bein^' reported. 



It is stated that the germinability of T'. faba was increased by previous ex- 

 posure to the Rontgen rays for a moderate period of time, but that it was 

 lessened by the longer exposures. The production of dry substance was in- 

 creased only in case of limited after-illumination. Longitudinal growth of the 

 aerial portion was somewhat increased in diminished light, great Individual 

 differences appearing in this series of tests. 



On the relation of root growth and development to the temperature and 

 aeration of the soil, W. A. Cannon {Amer. Jour. Bot., 2 (1915), No. 5, pp. 

 211-224. figs. 5). — The results of the direct aeration experiments on the re- 

 action of roots were not deemed entirely consistent, and these are to be reiu^sited. 



It appears from the results of tests as given that roots which lie close to the 

 surface of the soil are subject to the influence of an environment quite different 

 from that affecting the deeply placed roots. It is considered fair to assume 

 that the characteristic differences in mature root sj-stems are largely the results 

 of unlike responses to the environmental conditions. 



The root factor presents two phases, the root character itself and the man- 

 ner of response to the soil environment. In the former case, especially in obli- 

 gate deeply penetrating roots, the limiting factor appears to be only the depth 

 of the soil. In species having generalized roots and roots which are essentially 

 shallow growing the limiting factors relate to root re.'=;ponse to such environ- 

 mental features as moisture, aeration, and temperature. Species having plastic 

 roots or roots capable of response to a wide range of soil environment should be 

 more widely distributed than those less capable in these respects. This con- 

 clusion is said to have been supported by observations so far as they have 

 shown the true conditions. 



Studies on the transpiring power of plants as indicated by the method of 

 standardized hygrometric paper, A. L. Bakke (Jour. Ecology, 2 (1914), ^o. S, 

 pp. 145-118. figs. 2). — Employing the method of standardized cobalt chlorld 

 paper essentially as devised by Livingston (E. S. R., 28. p. 528), the author has 

 made a study of the daily course of foliar transpiration, the relation of position 

 and age of the leaves thereto, the relation of the diurnal to the nocturnal 

 foliar activity, transpiration as an Index of xerophytlsm or of mesophytism. 



