SOILS— FERTILIZERS. 521 



Do roots assimilate nitrates? P. Slezkin (Zhur. Opuitn. Agron. [Russ. Jour. 

 Expt. La 11(1 u:]. 9 ilOOS), Xo. 1, pp. 27-33, figs. 4).— The author conducted 

 vegetatiou experiments in vessels divided into 4 sections, each containing a 

 different nutritive solution, thus making it possible to transfer the roots of a 

 plant at different stages of growth from one solution to another. In one case a 

 long root fi-om a nitrate solution was so bent that it was partly immersed in 

 the nitrate solution and partly in a solution containing calcium phosphate. In 

 the latter solution new shoots soon appeared, while the part of the root in 

 the nitrate solution remained smooth as before. On the other hand, a root 

 from a solution containing calcium phosphate partly bent over into a nitrate 

 solution continued to strongly develop in the former, new shoots appearing and 

 old secondary roots growing considerably, while the part in the nitrate solution 

 did not increase in length and formed only rudimentary shoots. The conclusion 

 is drawn from these experiments that if the growth of the roots is an indica- 

 tion of independent assimilation, roots assimilate only phosphoric acid and do 

 not assimilate nitrates. 



Note on a toxic substance excreted by the roots of plants, F. Fletcher 

 iilcm. Dcpt. Agr. India, Bot. Scr.i 2 (1908), No. 3, pp. 16, pi. 1; abs. in Jour. 

 Chcin. Soc. [London], 9-'f (1908), No. 5-'i9, II, p. 617). — From observations on cot- 

 ton, sorghum, cajanus, and sesame grown side by side in field plats and on the 

 same crops, and wheat and gram, grown in water cultures, the conclusion is 

 reached that plant roots excrete a substance which is injurious to other crops. 

 This seems to be especially pronounced in case of sorghum. The results both 

 in the field and in water cultures indicate that the substances excreted by 

 various plants are identical. Chemical tests of the substances obtained in water 

 cultures indicate that they are alkaloidal in character. 



•' The amount of substance given out by the roots is not inconsiderable. For 

 instance, the precipitate obtained by adding potassium sulphate to a solution 

 containing the excrement of 10 cotton plants growing until their combined air- 

 dry weight was 0.4 gm. weighed, when dry, 0.21 gm. 



" Sesamum in its early stages of growth appears actually to excrete a greater 

 amount of material than it builds up in its own substance." See also a previous 

 note (E. S. R.. 19, p. 822). 



An alleged excretion of toxic substances by plant roots (Nature [London], 

 78 (1908), No. 2026, pp. .'f02, .'t03). — Reviewing recent investigations on this sub- 

 ject, including especially those of the Bureau of Soils of this Department and 

 of F. Fletcher, the conclusion is reached that " we can not consider that the 

 question of root excretion has been materially advanced in any of these 

 publications." 



The productiveness of the soil: Biological factors, J. M assart (Ann. 

 Gembloux, 18 (1908), No. 6, pp. 3.'P-3o3, pis. 6).— This is a review of work of 

 the Bureau of Soils of this Department on the relation of toxicity to fertility of 

 soils. For another article of this series see a previous note (E. S. R., 19, p. 

 1015). 



Further soil tests in paraffined wire baskets, B. L. Hartwell and F. R. 

 Pember (Rhode Island Sta. Bui. 131, pp. iJ-Ji).— This bulletin contains an ac- 

 count of a continuation of work previously reported in Bulletins 120 and 121 of 

 the station (E. S. R., 19, p. 317), " and concludes the comparison of the results 

 of soil tests in the field with those secured by the ' wire-basket method for de- 

 termining the manurial requirements of soils,' " which were made in cooperation 

 with the Bureau of Soils of this Department. 



" Results by the basket method, with soils from eight different localities in 

 the State during two seasons, are presented. In certain cases, first and second 

 trials have been made with the same soil during the same season, 



