AGRICULTURAL BOTANY. 229 



(E. S. R., 22, p. 721) the variations iu the quantity of pentosans present in 

 plants during the daytime and at night were especially investigated. 



In the plants (Vicia faia minor) examined, a tendency to an increase in the 

 absolute quantity of the pentosans during the day and a decrease during the 

 night was observed. It was also found that when sugar was furnished to the 

 leaves a marked increase in the quantity of pentosans occurred, while the ab- 

 sence of carbohydrate foods and of photosynthesis diminished the amount of 

 pentosans present in the plants. 



On the phosphorus and ash. content of the leaves of perennial plants, 

 G. Andre (Compt. Rend. Acad. Set. [Paris], 1^9 (1909), No. 1, pp. 45--i8; abs. 

 in ZentU. Agr. CJiem., 39 (1910), No. 7, pp. 458-460).— The results are reported 

 of investigations on the variations at diffei'ent periods in the year of the 

 phosphorus and ash present in the leaves of chestnuts. 



It was found that the phosphorig acid iu the leaves undergoes a marked 

 diminution during the movements of nitrogen toward the inflorescence, while the 

 phosphates soluble in water (mineral phosphates) are most abundant when 

 the leaves are very young. Lecithins were much increased as the flowering 

 period approached, and seemed to play a role in the osmotic phenomena which, 

 at this period, aid in the passage of the nitrogen in the leaves toward the 

 reproductive organs. The ash content was quite small and uniform during 

 the entire life of the leaves of the chestnut and was especially poor in silica. 



Some observations on the presence of free hydrocyanic acid in plants, 

 C. Ravenna and M. Tonegutti (Atti R. Accad. Lincei, Rend. CI. Sci. Fis., Mat. 

 c. Nat., 5. ser., 19 (1910), IT, No. 1, pp. 19-25).— The authors claim that the 

 usual methods used for detecting the presence of free hydrocyanic acid in 

 plants (destroying the enzyms present in the leaves by boiling water or boiling 

 alcohol) are untrustworthy, in that the enzym present in the leaves has time 

 before it is destroyed to form an appreciable quantity of hydrocyanic acid 

 from the glucosid present in the leaves. 



In the new method proposed, boiling caustic potash is used to destroy the 

 enzym, and the leaves are introduced into it one at a time, thus preventing a 

 lowering of the temperature. The leaves of the cherry laurel tested by this 

 method showed no trace of free hydrocyanic acid. 



As a result of other experiments it is claimed that the decrease observed in 

 the quantity of hydrocyanic acid found in air-dried leaves, compared to that 

 found in crushed leaves macerated for 24 hours, is not due to a volatilization, 

 but to a true assimilation of the hydrocyanic acid on the part of the leaves. 



A physiological-chemical research on the root tubercles of Vicia faba, 

 G. Sani (Atti R. Accad. Lincei, Rend. CI. Sci. Fis., Mat. e Nat., 5. ser., 19 (1910), 

 II, No. 4, PP- 207-211). — The author claims that at least two nitrogenous sub- 

 stances (asparagin and glycocoll) are elaborated by the bacteria in the root 

 tubercles and are directly available as a source of nitrogen for the host. 



The assimilation of nitrogen by certain nitrog'sn-fixing bacteria in the 

 soil, W. B. BoTTOMLEY (Proc. Roy. Soc. [London~\, Ser. B, 82 (1910), No. B 560, 

 pp. 627-629). — A report is made of further investigations (E. S. R., 22. p. 122) 

 on the fixation of free nitrogen in culture media and in soils by separate and 

 mixed cultures of Azotobacter chroococcum and Pscudomonas radicicola, the 

 former obtained from garden soil and the latter from the root tubercles of 

 beans and clover. 



After pure cultures of these two bacteria, separately and in combination, 

 were incubated for 10 days at 24° C. in suitable culture media, the nitrogen 

 content of the flask was determined, and the following averages obtained: 

 For Azotobacter alone, 2.19 mg. of nitrogen in 100 cc. per unit of carbohydrate; 



