732 EXPERIMENT STATION BECOED. [Vol.36 



2). — The authors report on a study of the effects of equimolecular proportions 



of manganous and ferric chlorids on the growth of two varieties of wheat plants 



in water cultures. Knop's solution was used as the culture medium, and two 



M M 



concentrations were employed of each salt, T'qqq and innnQQ • The study was 



limited to the antagonistic relations between manganese and iron in the belief 

 that the chlorotic effects due to manganese might indicate interference with the 

 role of iron in the production of chlorophyll. 



Attention is particularly called to the prevalence of the toxic effect of man- 

 ganese over iron at the low plane of supply. It is shown that for the growth 

 of roots even the low plane of manganous chlorid is toxic. When the higher 

 concentrations were used, ferric chlorid exerted stronger effects than mangan- 

 ous chlorid upon the growth and color of the varieties of wheat. 



Electromotive phenomena in plants, A. D. Waller et al. {Rpt. Brit. Assoc. 

 Adv. Set., 85 {1915), pp. 218-226, figs. 2). — This is a committee report of studies 

 by A. D. and A. INI. Waller, regarding investigations of the electrical measure- 

 ment of the vitality of vegetable tissues. In pursuance of experiments de- 

 scril)ed in a previous report (E. S. R., 32, p. 522), the authors have endeavored 

 to estimate the relative vitality of the plumules and radicles of seedlings by 

 measuring the voltage of the blaze currents excited by single induction shocks, 

 employing for this purpose seedlings of Hordeum vulgare. Tests were applied 

 to the separated plumule and the radicle respectively on the fourth and on the 

 sixth day of germination. The results are given in tabular detail. 



Alterations of temperature are said to give rise to considerable alterations in 

 the magnitude of blaze currents and of electrical conductivity, so these obser- 

 vations were made within the range of 18 to 20° C. The seeds must be soaked 

 for a certain time before they will give off their full blaze current. The elec- 

 trical response of a plumule of H. vulgare is of considerably higher voltage than 

 that of a radicle. In consequence of excitation, the electrical resistance of a 

 plant is diminished. The diminution is attributed to the chemical dissociation 

 which has given to the blaze current. It is greater after strong than after 

 weak excitation and the increased conductivity appears to be in relation with 

 the magnitude of the previous blaze current. 



The work during 1915 was intended to ascertain whether the blaze currents 

 can be used as a practical test of the germination value of seeds. The result 

 of such tests to peas are considered to show that an average blaze current of 

 0.03 or 0.04 volt indicate a high class seed, of which about 97 per cent would 

 germinate, individual peas out of the series tested ranging in response from 0.01 

 or 0.02 to 0.07 or 0.09 volt. The electrical test is much quicker than the germi- 

 nation test and is thought likely to become a practical means to ascertain 

 quickly the germination value of seeds in the market. The authors are still 

 engaged In making tests on different varieties of seeds. 



Tlie effect of electrical stimulus on the permeability of plant cells, R. 

 KoKETSU {Bot. Mag. [Tokyo], 30 {1916), No. 355, pp. 26^-266).— Experiments 

 are briefly noted in which it is claimed to have been shown that, by the applica- 

 tion of electrical stimulus, the plasma membranes of epidermal cells are ren- 

 dered more readily permeable to dissolved substances. 



The influence of defoliation on the development of sugar beet, H. Pellet 

 (Bui. Assoc. Chim. Sucr. et Distill., S3 (1916), No. 7-9, pp. 150-161, figs. 2).— It 

 is considered as proved, by the tests here described, that defoliation of beet 

 influences the weight and sugar content of the root. This result is more marked 

 as removal of the leaves is more frequent and more complete, the production 

 of the new leaves thus drawing upon the materials in the root. 



