720 EXPEEIMENT STATION RECOED. 



AGRICULTURAL BOTANY. 



Vegetation and frost, F. F. Blackman {.New Phytol, 8 {1909), No. 9-10, 

 pp. 35'f-.iGS). — 'J'be author gives a suuiuiary of the i)resGnt state of our knowl- 

 edge regarding the action of frost on vegetation. The old idea of Sachs that 

 the injury was due to the subsequent I'apid thawing has been shown to be 

 erroneous by Molisch. Mez holds that the jn'otoplasni of the plant is directly 

 susce])til)Ie to cold and thiit each cell has a fatal niiniminn temperature. Gorke 

 showed that freezing causes a precipitation or " salting out " of some of the 

 soluble i)roteids and that the tenip<'rature reiiuirinl for this purpose varies 

 widely with different species of plants, begonias that are injured by a temi)era- 

 ture of — 5° C. having part of their protein precipitated at — 3°. Winter rye 

 showed the effect of cold at — IS'' and pine needles at — 40°. 



Ijidforss has recently found an agency in plants that protects them against 

 cold. He finds that all winter-green leaves are quite free fi-om starch but con- 

 tain sugar and oil in the mesophyll. In the sunmier these same leaves contain 

 abundant starch. This they regenerate in the spring, or if the plants are 

 brought from the open into a warm room starch is also abundantly formed from 

 sugar. The only exception found by him was in sultmerged plants, which show 

 starch throughout the winter. By means of experiments he has shown that the 

 sugar in the cells not only aids in keeping down transpiration but also enables 

 the plants to withstand lowered temperatures. 



Another phenomenon which seems to be explained by Lidforss's work is the 

 frequent killing of trees early in the spring after they have endured the pro- 

 longed cold of winter. This is held to be due to the fact "that a succession of 

 warm days causes the regeneration of starch, making the plants more sus- 

 ceptible to sudden cold. This fact was also borne out by observations that it 

 is the south side of trees and shrubs that suffer most from winter injury. 

 The theory of Lidforss is that sugar has a protective action in that it retards 

 the salting out effect reported by Gorke. 



The occurrence of sugar and oil in winter in the periderm of tree trunks has 

 also been reported. 



Chemical investig-ations on germination, N. T. Deleano (Arch. Sci. Biol. 

 [St. Pctcr.sJ).], 15 (1910), No. 1, pp. 1-2.',; Centhl. BwM. [etc.], 2. AM., 2ff 

 (1909), No. 5-7, pp. 130-11,6). — A study has been made of some of the more 

 important chemical changes taking place in the germination of oil-bearing seeds. 



After a resume of previous publications on the subject, the author describes 

 his experiments with castor bean seeds. He found that the phenomena con- 

 nected with the disappearance of fat are not confined to the outside of the cells. 

 The fat content of seeds was fairly well maintained for the first 8 days of the 

 experiments, after which saponification proceeded with great rapidity. He 

 concludes that iiractically all the fat in oil-bearing seeds is saponified outside 

 of the cells in which it is held as reserve. 



In relation to the acidity observed during germination, the author was able 

 to recognize acetic and lactic acids only. The lactic acid was formed during 

 the transformation of the oil, and it is thought to be very probably a secondary 

 product of the fat oxidation. The amount of lactic acid seemed always to be 

 fairly constant, and it is belieA'ed that the surplus disappeared by the forma- 

 tion of new combinations. 



Studies were also made of the catalase, peroxidase, and other enzyms and 

 their role in the germination of the seed. 



Light germination, W. Kinzel (Her. Detit. Bot. GeselL, 27 (1909), No. 9, 

 pp. 536-545, pi. 1). — The author records a large number of germination tests 



