AGEICULTURAL BOTANY. 827 



and other included materials upon plants, tlie observations being made in the 

 public parks of Chicago, in Pittsburgh and vicinity, along the railroad between 

 Tyrone and Pittsburgh, and at State College, Pa., the work being carried on 

 cooperatively between the botanical department of the Pennsylvania State Col- 

 lege and the Institute of Industrial Research. 



The experiments show that especially in the case of pines, when soot is ap- 

 plied in small quantities over a considerable interval of time measurable injury 

 follows. The soot is found to be a mixture of finely divided carbon, ash, tar, 

 and gases, which may have a mechanical effect and also cause injury through 

 their chemical properties. The injury done by soot Is considered chiefly due 

 to the accompanying ash, tar, and gases. Of the gases, sulphur dioxid and 

 sulphur trioxid were said to cause considerable injury to vegetation. 



The injurious effects of tarring roads on neighboring plants and remedies 

 therefor, C. L. Gatin (1. Cong. Internat. Pathol. Comparic [Paru], 1912, vol. 

 2, Comp. Rend., pp. 914^-924)- — ^This work has already been partly reported 

 (E. S. R., 27, p. 333). Strong insolation is said to favor injury to plants by 

 gases from tarred roads, while frequent rains or strong winds decrease its 

 severity. 



Bacterial digestion of fiber or cellulose (Wisconsin Sta. Bui. 2^0 (1914), 

 pp. 21, 22, fig. 1). — In an investigation conducted by R. R. Primm, a method 

 was perfected whereby bacteria capable of digesting fiber or cellulose are readily 

 isolated and studied. It is claimed that bacteria have been isolated which 

 actively digest cellulose at a temperature of 149° F., and that they have been 

 kept in pure cultures for a number of generations at this temperature without 

 the loss of their cellulose digesting power. 



Influence of soil bacteria on plant growth (Wisconsin Sta. Bui. 240 (1914), 

 pp. 19-21, fig. 1). — In a study of the injurious effect of certain soil compounds 

 on plant growth, C. Hoffmann found that when pure cultures of various soil 

 bacteria were grown in extracts from marsh soil in which corn, oats, or clover 

 had been previously grown, the bacterial content was considerably increased. 

 When, however, the organisms were grown in extracts from cropped loam or 

 sandy soils, the bacterial development was retarded. The action of corn 

 grown in such solutions was especially notable in its root development. It was 

 also found that different kinds of bacteria behaved differently in previously 

 sterilized soil, showing apparently that the resulting compounds of bacterial 

 activity in soils have an important bearing on plant nutrition and that various 

 crops stimulate or retard others through this means, as in crop rotation. 



Physiological investigation of the respiration of denitrifying micro- 

 organisms, A. F. Lebedev (Zap. Nov. Obshch. Test., Vol. 39; ahs. in Zhur. 

 Opytn. Agron. (Russ. Jour. Expt. Landw.), 13 (1912), No. 4, pp. 632, 633). — 

 The process of denitriflcation was studied in the case of Bacillus pyocyaneus 

 under anaerobic conditions. 



The examination of the gaseous exchange in old cultures showed the ratio of 

 carbon dioxid to nitrogen to be equal to the theoretical one or very near to it. 

 Thus the denitrification process is a true respiratory process. However, in 

 young cultures this ratio is always greater than the theoretical one, being in 

 some cases even IJ times as great. 



A contribution to our knowledge of the relation of certain species of 

 grass-green algae to elementary nitrogen, J. R. Schbamm (Ann. Missouri Bot. 

 Gard., 1 (1914), No. 2, pp. 157-184, pi- 1, fig- 1)- — In the present series of experi- 

 ments it was the author's aim to extend the observations over a greater variety 

 of algal forms than has been dealt with heretofore in pure culture and under 

 unexceptionable conditions. It is claimed that in seven forms named complete 

 results have been obtained, none of these forms being able to fix free atmos- 



