AGRICULTURAL BOTANY. 139 



The action of vapors on green plants, M. Mirande (Contpt. Rend. Acad. Sci. 

 [Paris], 151 (1910), No. 7, pp. //Si-^8^).— According to the author, it has been 

 known for some time that etherization, freezing, ultraviolet rays of light, dry- 

 ing, etc., will cause the blackening of plant tissues and, under certain condi- 

 tions, the liberation of A'olatile substances that have been previously localized 

 in the plant but are set free through the agencies mentioned. 



A study has been made of the action of numerous substances on the blacken- 

 ing of the cherry laurel and on the liberation of hydrocyanic acid, which is 

 given off from the leaves of that plant. Various hydrocarbons, alcohols, phenols, 

 acids, ethers, aldehydes, cetones, amins, and amids were tested, some of which 

 blackened the plant and liberated hydrocyanic acid, others caused a change in 

 color but no acid was set free, while still others showed no effect whatever. 



The property of blackening plants and liberating volatile substances is said 

 to be possessed by various organic compounds the stereochemic structure of 

 which differs w^idely. 



Investigations on the blackening of leaves, L. Maquenne and B. Demoussy 

 (Bui. Mus. Nat. Hist. Nat. [Paris], 1010, No. 1, pp. SI, 38).— Attention is called 

 to the fact that leaves are often blackened under the influence of electric light, 

 and the authors have carried on investigations to determine the cause of this 

 phenomenon. 



Plants were subjected to the action of a mercury lamp, the light of which is 

 very rich in ultraviolet rays. When plants with a thin epidermis were exposed 

 to this light the leaves were blackened within 2 or 3 hours, while if the 

 epidermis was rather thick it required 10 to 12 hours to produce such an effect. 

 The action of the ultraviolet rays seems to result in the destruction of the 

 protoplasm of the cells of the plants, and the effect of these rays on plants is 

 quite similar to that on animals, micro-organisms, fungi, etc. 



Heat was found to exercise a similar effect. Leaves of the fig, lilac, privet, 

 and aucuba when plunged in water at temperatures of 65 to 70° for half a 

 minute turned black in about an hour. If placed in boiling water for a second a 

 similar effect was produced, but if they were allowed to remain for 2 minutes, 

 blackening did not occur except in the case of the aucuba. 



The experiments seem to indicate that the action is a diastatic one and is 

 generally due to the effect produced on the oxidase following the destruction of 

 the protoplasm. 



Some observations on catalase, C. O. Appleman {Bot. Oaz., 50 (1910), No. 3, 

 pp. 182-192, fig. 1). — During the course of an investigation on the physiological 

 behavior of enzyms in the after-ripening of the potato tuber, the author found 

 it necessary to investigate methods for the quantitative determination of cata- 

 lase in this organ. After giving an account of the distribution and function 

 of catalase, the methods adopted are described at considerable length. 



It was found that there was an insoluble and a soluble catalase in the potato 

 which could be separated by ordinary filter paper, approximately 50 per cent 

 passing through it. None, however, would pass through a Chamberland-Pas- 

 teur filter. 



Potato catalase was found to be limited in its effect on the decomposition 

 of hydrogen peroxid, a given amount of catalase apparently being required to 

 decompose a definite amount of hydrogen peroxid. The catalase activity was 

 found to bear a relation to the respiratory activity of the potato, decreasing 

 under the same conditions as did the respiration. 



The physiology of lipoids, W. Palladin (Ber. Deut. Bot. Gesell., 2S (1910), 

 No. 5, pp. 120-125).— A report is given of investigations conducted with wheat 

 seedlings to determine the physiological role of lipoids in plants. 



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