432 EXPEEIMENT STATION KECORD. [Vol. 36 



and alkaline solutions with different forms and quantities of iron and the 

 effect of the reaction of the solution on the assimilation of iron was noted. 



When judged by the growth of plants, ferrous sulphate, ferric citrate, and 

 ferric tartrate afforded sufficient iron when used in proper quantities in acid 

 and neutral solutions. Ferric chlorid proved an inferior source of iron and 

 dialyzed iron utterly inadequate. Ferric tartrate was the only form of iron 

 which furnished sufficient amounts of that element for the nutrition of plants 

 in alkaline solutions. 



Plants grown in acid solutions contained the highest percentages of iron. 

 Those grown in neutral solutions contained higher percentages of iron than 

 those grown in alkaline solutions when some forms of iron were used, but they 

 contained equal percentages when other forms were used. The percentages of 

 nitrogen, phosphoric acid, lime, magnesia, and carbon-free ash in plants grown 

 in six different solutions did not vary appreciably when compared with the iron 

 content. 



It appears that rice was not found to be particularly sensitive to the reac- 

 tion of the solution except as the reaction influenced the availability of the 

 iron. This is believed to substantiate previous work in showing that lime- 

 induced chlorosis is caused by a lack of iron and in indicating that the only 

 acton of carbonate of lime in inducing chlorosis lies in its diminishing the 

 availability of iron. 



The influence of manganese on plants, G. IMasoni (Stas. Sper. Agr. Ital., 

 48 {1915), No. 10-11, pp. 822-838; abs. in Chem. Abs., 10 (1916), No. 19, p. 

 2495; Intermit. Inst. Agr. [/2owe], Internat. Rev. Sci. and Pract. Agr., 7 (1916), 

 No. S, pp. 845, 5^6).— Reporting a further study (E. S. R., 26, p. 226) of maize 

 as affected by manganese compounds, the author states that manganese in very 

 small or larger proportions has shown some favorable influence on the growth 

 of plants, but that this influence is not specific or direct. 



The nutrition of green plants by means of organic substances, C. Ravenna 

 (Atti R. Accad. lAncei, Rend. CI. Sci. Fis., Mat. e Nat., 5. ser., 25 (1916), I, 

 No. 9, pp. 649-655, figs. S). — The author, describing experiments carried out 

 with sterile cultures of maize in aqueous solutions of glucose, states that the 

 leaves produced starch even in the absence of carbon dioxid but only in the 

 light, the portion of the solar spectrum most influential in this regard being 

 that showing the greatest activity in regard to chlorophyll. The plants rooted 

 in sugar solution but deprived of carbon dioxid and of oxygen did not form 

 starch even in sunlight. 



The cause of the disappearance of cumarin, vanillin, pyridin, and quinolin 

 in the soil, W. J. IIobbins (Science, n. ser., 44 (1916), No. 1147, pp. 894, 895).— 

 A preliminary report is given of a biological study made to determine the reason 

 for the disappearance of the toxic activity of cumarin, vanillin, pyridin, and 

 quinolin in soils. 



Flasks containing soils to which the above compounds had been added were 

 inoculated with infusions from normal soils and incubated for two months, 

 after which wheat was planted in the soils. The growth of the wheat plants 

 in the inoculated soil showed that the toxic properties of the compounds had 

 largely disappeared, while their effect was still very evident in bottles contain- 

 ing sterile soil. This is believed to indicate that the disappearance of the com- 

 pounds is due to biological causes. From the bottles or pots, three species of 

 bacteria were isolated, one of which was found to use pyridin as a source of 

 nitrogen, while one used vanillin and another cumarin as a source of carbon. 

 No organism has yet been found to act on quinolin. 



As a result of the author's Investigations, it Is considei'ed that the enormous 

 increase in the number of organisms in the treated pots and the disappearance 



