1916] AGRICULTURAL BOTANY. 25 



Activities of the micro-organisms of the soil (North Dakota >S7«. Rpt. 11)15, 

 pt. 1, pp. 16, 17). — A study is in progress to determine and control the optinuirn 

 conditions for tlie maximum efficiency of micro-organisms concerned in soil 

 fertility. The work of the past year is said to have demonstrated that the 

 energy material, consisting mainly of carbohydrates and their deconiitosition 

 products, is the chief factor governing amnionification. As long as readily 

 available energy material is present in excess of the required ratio to nilrogon 

 demanded by ammonifying organisms, a minimum amount of nitrogen will be 

 accumulated. However, when the readily available amount of energy ma- 

 terial falls below the necessary ratio to nitrogen required by ammonifying 

 organisms, the phenomena of aramonification will take place, although, if the 

 energy material becomes too low, the ammonifying phenomena will be almost, 

 If not entirely, lost. 



As a result; of this study, it is believed that ammonification is a doubtful 

 criterion for measuring soil fertility. 



Fission fungi which decompose urea and form nitrates, M. DIjggeli 

 (Xatunc. Wchnschr., 30 {1915), No. 20, pp. 305-315) .—This is a somewhat gen- 

 eral discussion of the biology of some fission fungi and the chemical changes 

 connected with their activities. 



Enzym action in the marine algae, A. li. Davis (.l«n. Missouri Bot. Card., 2 

 (1915), No. If, pp. 771S36). — Difficulty having been experienced in demon- 

 strating enzym action in Fucus vcsiciilosus (E. S. R., 30, p. 72S), the investiga- 

 tion was extended to certain representative forms of the three great groups of 

 the marine algae in order to ascertain whether this apparent inactivity is charac- 

 teristic of the algae and to add to the knowledge of the general metabolism of 

 the group. 



The data obtained are thought to show that the number of enzyms in algje 

 that can be isolated by standard methods is small. This seems to l)e true espe- 

 cially of the brown algif. The enzyms which were found in fresh or dried algal 

 tissue include carbohydrases hydrolyzing the polysaccharids, starch, dextrin, 

 glycogen, and laminarin, but not those hydrolyzing the several disaccharids em- 

 ployed as substrates ; lipases acting upon neutral fats but not upon the esters 

 of the lower fatty acids ; proteinases ; nucleases ; oxidases and peroxidases ; and 

 catalases. Negative results were obtained from cellulase, cytase, maltase, lac- 

 tase, sucrase, amidase, and esterase. The action of all the enzyms isolated was 

 very slow. 



An extensive bibliography is given. 



On the action of pectase, N. G. Ball (Sci. Proc. Roy. Dublin Soc, n. ser., 

 U (1915), No. 28, pp. 349-357, fig. i).— This is an attempt to study the action 

 of pectase by observing the electrical conductivity of a solution of pectin obtained 

 from roots of Daucus carota when acted upon by the enzym, and also by deter- 

 mining the change in viscosity. 



It has been found that during the action of pectase on the solution of pectin 

 the electrical conductivity of the solution remains constant, indicating the forma- 

 tion of a gel and not merely a very viscous liquid. The activity of the enzym 

 is much greater at 14° C. than at 0°, as evidenced by changes in viscosity during 

 coagulation. The viscosity was found to increase slowly at first, then more 

 rapidly to a maximum, followed by a rapid decrease. Increase of electrolytes 

 present lowered the maximum, while a decrease raised it. The decrease in 

 viscosity is thought to be explainable by the action of the electrolytes in clump- 

 ing together the particles of colloid forming the reticulum of the gel, so that a 

 suspension is produced. 



Osmotic pressures in plants. — IV, On the constituents and concentration 

 of the sap in the conducting tracts, and on the circulation of carbohydrates 



