AGRICULTURAL, BOTANY. 223 



that the proportion of soluble nitrogen to total nitrogen increased in the 

 abnormal growths due to the presence of the insects. An examination of etio- 

 lated leaves showed a similar condition, and attention is called to the possible 

 correlation between the increase of soluble nitrogenous materials and the dimi- 

 nution of chlorophyll. 



Some experiments on the utilization of ammonium salts by green plants, 

 E. Pantanklli and G. Severini {Staz. Sper. Ayr. Itiil., .'^3 (HJIO), No. 6, pp. hk9- 

 S.'i'i). — The authors review quite fully the work of other investigators on the 

 comparative fertilizing value of difCerent forms of nitrogen and the conditions 

 which they produce in soils, and report the results of experiments on the util- 

 ization of different ammonium salts by green plants grown in sterilized liquid 

 cultures, in sterilized soils of different structure and each having a different 

 absorbing power, and in soils under normal crop conditions. The salts used 

 were sodimn nitrate (for comparison), ammonium tartrate, nitrate, sulphate, 

 and chlorid, triammonium phosphate, and ammonium magnesium phosphate, 

 while wheat, rice, mustard, corn, and flax were the plants used. 



Detailed tabulated data are given of the resulting acidity or alkalinity of the 

 culture media for the various ammonium salts used during the period of growth 

 of the plants, both in the water and pot cultures. The amounts of organic, 

 ammoniacal, and nitrate nitrogen obtained or used during the growing period of 

 the plants are recorded. The general effects of each salt on the growth of the 

 different plants are also noted. 



It was found that in liquid cultures, under conditions in which nitrification 

 was excluded, certain ammonium salts are able to act as a source of nitrogen 

 food for green plants. A rapid absorption of the ammonium cation induces an 

 acidification of the nutritive liquid, which reaches a maximum during the first 

 period of growth for those salts of ammonium derived from strong acids, such 

 as sulphuric, hj-drochloric, nitric, and phosphoric acids. If the anion is ab- 

 sorbeil rapidly, as is the case with the nitric and phosphoric anions, after the 

 first week of growth the external acidity diminishes and the plants grow vig- 

 orously. By using an ammonium salt which is only slightly soluble, such as 

 ammonium magnesium phosphate, this danger of acidification is avoided. More- 

 over, the absorption of the ammonium is thereby much decreased, giving the 

 plant time to utilize it in the best possible manner for the production of organic 

 substances and of albuminoids. Especially is this true of wheat, maize, and 

 rice. In sterile soils where nitrification is excluded, the different salts of 

 ammonium act differently under the influence of two principal factors, viz, the 

 diverse absorbing power of the soil for the ammonia, and the presence of lime 

 in the soil in sufficient quantities. 



Briefly, the authors conclude that the Inferiority usually attributed to 

 ammonium sulphate as compared to nitrate of soda as a source of nitrogen 

 results from irrational application to the soil or to crops to which it is not 

 suited, and does not justify a general depreciation of ammonium salts as a 

 source of nitrogen food for green plants; that ammoniacal nitrogen has a co- 

 efficient of utilization for the formation of organic nitrogenous compounds 

 superior to that of nitrate nitrogen; and that the utilization of a salt of 

 ammonium depends upon the relative rapidity of the absorption of its two ions. 



Investigations on nitrogen assimilation in green leaves, R. Otto and W. D. 

 KooPEB {Landw. Jahrh., 39 (1910), No. 6, pp. 999-100-^) .—The author gives the 

 results of experiments with the leaves of JEsculiis hippocastanum as to their 

 ability to fix free nitrogen. 



Fresh leaves were cut from the plant and the stems placed in distilled water. 

 Tests were then made for the nitrogen content of these leaves every morning 

 101861°— No. 3—11 3 



