1917] CURRENT LITERATURE 349 
would have converted into a permanent forest. A neglect of this attention 
resulted in the complete failure of the project.—Gro. D. FULLER. 
Nitrogen relations of semi-arid soils —McBrtu® finds that semi-arid soils 
fail to nitrify dried blood when it is added in 1 per cent quantities. Under the 
conditions ammonia accumulates in the soil and 50 per cent of the nitrogen 
may be lost to the air (probably as ammonia) within 6 weeks. When added at 
ordinary fertilizer rates nitrification is complete. With green manures, espe- 
cially legumes, nitrification is rapid. Fifty per cent of the nitrogen of the green 
manure is transformed to nitrates in 30 days. Furrow irrigation leads to the 
accumulation of the larger part of the nitrate in the surface 6 inches of the soil, 
and this often results in niter spots. Overhead or basin irrigation gives far 
better results. Mottled orange leaves show higher water content than checks, 
and extreme mottling is often, yet not invariably, associated with high nitrate 
content.—Wwa. CROCKER. 
Effect of dust on photosynthesis.—The effect of surface films and dusts on 
physiological processes in plants has aroused considerable interest in recent 
years. California citrus vegetation in the neighborhood of cement works 
this fact to determine the effect of dusts on rathohydrate synthesis. He found 
that the cement dust in some cases shuts out as much as 80 per cent, of the light 
- from the upper surface of the leaf, but this high exclusion of light did not 
interfere with carbohydrate synthesis. This work bears out in a practical and 
interesting way that of Brown and EscomseE in showing the small amount of 
light that is really necessary for carbohydrate synthesis.—Cuas. O. APPLEMAN. 
Nitrogen fixation—The question of nitrogen fixation by filamentous 
fungi has been = thee smb by Duccar and Davis* with reference to Asper- 
gillus niger, Macrosporium commune, Penicillium digitatum, P. expansum, 
Glomerella Gossypii, and Phoma Betae. Of these, Phoma Betae was the only 
form which was definitely shown to be capable of fixing free nitrogen. The 
quantities fixed by this fungus varied from 3.022 to 7.752 mg. per culture of 
5occ. of solution when sugar beet or mangel decoction with added sugar 
were used as culture media. The authors give a critical review of all the 
available literature on the subject, and in their own work exercised every pre- 
caution to avoid the errors and faulty methods which have led to the numerous 
conflicting results in the investigations of this problem.—H. HAssELBRING. 
# McBeth, I. G., Relation of the transformation and distribution of soil nitrogen 
to the nutrition of citrus plants. Jour. Agric. Research 9:183-252. figs. 19. 1917- 
# Younc, H. D., Studies on the relation of cement dust to citrus vegetation. 
I. The ack on photosynthesis. Biochem. Bull. 5:95~100. 1916. 
“4 Duccar, B. M.; and Davis, A. R., Studies in the physiology of the fungi. 
I. Nitrogen fixation. Ann. Mo. Bot. Gard, 3°413-437- 1916. 
