34 EXPEEIMENT STATION EECORD. 



tiou would have no effect upon respiration, and tliat explanation for any 

 acceleration of growth must be sought in other functions of the plant. 



The gaseous products of electrical discharge in air are said to have no effect 

 upon germinating peas but are deleterious to young seetllings. 



Experimental and critical studies on freezing and frost killing in plants, 

 N. A. Maximow (Jahrh. Wiss. Bot. [Pringshcim], 53 (1914), No. 3, pp. 327-^20, 

 figs. 6). — Reviewing briefly previous communications by himself (E. S. R., 28, 

 p. 630) and others on the death point of plant cells as related to composition, 

 concentration, and freezing points of the contained or containing solutions, the 

 author gives details and results of his more recent studies, concluding that 

 killing by cold is probably due not simply to low temperatures as such (im- 

 plying a specific temperature minimum), but to physico-chemical changes set 

 up in the plasma colloids during the formation of ice therein. A bibliography is 

 appended. 



A study of the effect of smoke and dust on plants, V. Sabachnikoff iCon- 

 trihution d, VEtude (les Fumies ct des Poiissi^res Industrielles dans Icurs 

 Rdpports avec la Y6g6taUon. Thesis, Univ. 'Nancy, 1913, pp. 252, pis. 10, figs. 

 8). — The author gives a critical review of available literature on the subject, 

 describing in detail some of the recent investigations conducted in Germany, 

 Austria, and France. 



An account is also given of his investigations on the effect of sulphuric acid 

 in the air on the vitality and reproductive power of pollen and on the develop- 

 ment of grain in wheat. Oi^en flowers and gro^^ing heads of wheat plants 

 were placed within asi«rators and atmospheres containing known quantities of 

 sulphuric acid were drawn over them. It was found that exposure for more 

 than 24 hours to a concentration of more than 1 : 13,000 parts of sulphuric acid 

 was fatal to the action of pollen and a proportion in excess of 1 : 30,000 was 

 detrimental to the reproduction of plants. In the experiments viith wheat at 

 the time of flowering, sulphuric acid 1 : 10,000 completely prevented seed forma- 

 tion. A concenti'ation of 1 : 30,000 notably reduced the average number and 

 weight of the seed formed. Diminution in average weight was in proportion 

 to concentration of sulphuric acid. The injury is considered to be largely 

 confined to the reproductive organs of the plant. 



A bibliography of more than 200 titles is given. 



The occurrence of rennet in Rhizopus nigricans, M. Dubandard {Compt. 

 Rend. Acad. Set. [Paris}, 158 (1914), ^^o. 4, pp. 270-272).— The author reports 

 experiments which demonstrated the presence of an active rennet in the 

 mycelium of R. nigricans that rapidly coagulated milk at proper temperatures. 

 The optimum temperature for the activity of the enzym was about 50° C. 

 with a cessation of activity at 10°, and at 60° it was entirely destroyed. At 

 a temi>erature of 55° the enzym required 50 times as long a period to bring 

 about the coagulation of milk as was needed at the optimum temperature. 



On the presence in leaves and flowers not containing anthocyanin of 

 yellow pigments which may be transformed into anthocyanin, R. Combes 

 {Compt. Rend. Acad. Sci. [Paris], 158 {1914), ^"o. 4, pp. 272-274)-— In con- 

 tinuation of his studies on the autumn coloration of Ampelopsis hederacea 

 (E. S. R., 30, p. 729) the author has investigated a number of other plants to 

 determine whether anthocyanin is formed by the transformation of other 

 pigments. Studies were made of privet, several varieties of grapes, the foliage 

 of some of which redden in autumn while others turn yellow, and of narcissus, 

 the flowers of which contain a yellow pigment. 



In the case of privet and the varieties of grapes that redden on the approach 

 of winter, the red color is brought about by the oxidation of the yellow pigment 



