AGRICULTURAL BOTANY. 131 



number of species of trees is described at length and the relative injury to the 

 different species indicated. 



The author states that from the two years' observations there seems little 

 doubt that hail injury increases the infestation of hardy catalpa by the dry rot 

 fungus {I'oli/stivtiis versicolor). It was further found that it reduces the 

 annual wood increment, causing the formation of false annual rings in the 

 species worst affected. Natural pruning of the branches continues for many 

 years after a hailstorm has passed, and such pruning has been noted on branches 

 which had been injured 19 years previously. 



The post-mortem blackening' of leaves, L. Maquenne and B. Demoussy 

 (Rrv. Gdn. ScL, 21 {1910), No. 3, pp. 196-203, figs. 3).— A study has been made 

 of the cause of blackening of leaves after they are severed from the plant, and 

 while this phenomenon is found due to several causes, one of the most common 

 is the action of certain diastases on glucosids in the leaves. While the leaves 

 are living there appears to be no interaction of these substances, but upon the 

 death of the leaves the cell walls appear to become permeable and the change 

 of color rapidly follows. 



The intensity of alpine light, F. E. Clements and F. K. Butters {Abs. in 

 Science, n. ser., 31 {1910), No. 191}, p. If35). — Readings were made during the 

 summer of 1909 in the Selkirk Mountains, on Mt. Rainier in Washington, and 

 in the Rocky Mountains in Colorado to determine whether mountain regions 

 with higher humidity would reveal greater light absorption. The readings in 

 in the different regions were in close, if not complete, agreement, and indicated 

 that alpine light is little if any stronger than the light at lower altitudes and 

 that it can not be considered an efficient cause of alpine dwarfing. 



Action of ultraviolet rays on microbes, P. Cernovodeanu and V. Henri 

 {Compt. Rend. Acad. Sci. [Paris], 150 {1910), No. 1, pp. 52-5-'f; alts, in Jour. 

 Soc. Chem. Indus., 29 {1910), No. 3, p. 171).— A study of the bactericidal action 

 of ultraviolet rays emitted by mercury vapor lamps is reported. 



Action of ultraviolet rays on microbes, P. Cernovodeanu and V. Henri 

 {Compt. Roul. Acad. Set. [Paris], 150 {1910), No. 11, pp. 729-737 ) .—This is a 

 report of further investigations on the bactericidal action of ultraviolet rays 

 (see above). 



On the presence of enzyms in soil, water, and dust, C. Fermi {Centbl. 

 Bwkt. [etc.], 2. AM., 26 {1910), No. 10-12, pp. 330-33^) .—The methods used in 

 doterniiniiig the presence or absence of various enzyms in soil, water, and 

 dust are given, together with the results obtained for each case. Gelatinolytic 

 enzyms were more abundant in soil and dust than in water, while coagulant 

 enzyms were found in soil, water, and dust, but only in samples rich in decaying 

 organic matter. 



Proteolytic enzyms, amylase, invertase, and amygdalase were not found in 

 any of the samples. 



Tests with cultures of root tubercle bacteria, A. J. Ewart {Jour. Dept. 

 Afjr. Victoria, S {1910), No. 2, pp. 98-105, figs. //)! — This paper gives the results 

 of tests made with cultures of root tubercle bacteria, such as nitragin, nitro- 

 culture, etc. 



The cultures used were purchased in the open market, one being guarantied 

 to contain bacteria for the inoculation of field peas {Pisiim arvense) and the 

 other for alsike clover {Trifolium hiihridum). They were tested in the first 

 instance by using field peas grown in sterilized, artificial solutions, in which 

 No, 1 was inoculated, No. 2 uninoculated, and No. 3 inoculated but with no 

 nitrates in the nutrient solution. The peas grown in the uninoculated culture 

 were distinctly larger than in the other two, while root tubercles were found 

 on only No. 1. 



