AGRICULTURAL BOTANY. 825 



paltniarsh plants. The greater the physiological drought under which the 

 plants are accustomed to grow the greater will be the osmotic strength of the 

 sap in the turgid cell. For any locality the osmotic strength will vary with the 

 physiological scarcity of water. In all plants growing under the same conditions 

 ihe osmotic strength of the cell sap is practically the same. Where marked 

 differences in structural arrangements for checking loss of water ])y transpira- 

 tion are present the plants with the less adequate anatomical provision for trans- 

 jiiration will have the greater strength of cell sap. The effect of increasing the 

 osmotic strength of sap on absori)tion is very marked, the rate of absori)tion 

 of water being proportional to the osmotic strength of the .sap. The effect of 

 increased temiierature is also quite appreciable and tends to enhance the power 

 of absorption of water by plants. 



On the transpiration current in plants, II. 11. Dixox (Proc. Roy. 8oc. 

 \Loti(lon'\, So: B, 79 (1907), No. B 528, pp. -',1-57, fif/s. .5).— The author criticises 

 a paper by Ewart (E. S. R., 17, p. 958), pointing out objections to the methods 

 of investigation presented, and in addition he gives further arguments athrming 

 the cohesion theory of Dixon and Joly regarding the trans])irntion current in 

 plants (E. S. R., 7, p. 560). 



The effects of mag-nesium sulphate upon seedlings, Gertrude Burlixg- 

 HAM (Ah-s. in ^Science, ii. nrr.. .11 (V.JOl), No. 6.3S, p. .'i52). — A report is given of 

 extended experiments to test the ett'ect of dilute solutions of magnosium sulpluite 

 on seedlings. It was found that while magnesium sulphate is usually toxic in 

 strengths greater than 0.00.3 per cent, in weaker solutions it pi-oduces a decided - 

 stimulating effect, reaching a maximum in dilutions of 0.00075 to 0.00018 per 

 cent. Beyond this point the action gradually diminishes. 



Seedlings allowed to grow for several weeks in a dilute solution of magnesium 

 sulphate which was at first slightly toxic, finally developed strong lateral roots 

 and attained a root growth far beyond the controls. This seems to show that 

 magnesium sulphate in proper dilution is beneficial to the growth of seedlings, 

 and that any inhibitory effects are due to the presence of excessive amounts, 

 thus controverting Loew's theory that magnesium salts when alone in solution 

 are alw.ays injurious to plant growth. 



The effects of salts of some rare elements on seedlings, Alice A. Knox 

 and W. II. Welker {Abs. in Science, n. ser., 25 {1907), No. 63H, p. .}6/).— Salts of 

 a numlKU- of rare elements were tested on seedlings. The greatest molecular 

 concentration points at which growth occurred during the first 24 hours were 

 noted, as well as the least growth. It was found that the increase in toxicity 

 followed Mendeleefs table almost mathematically, the toxicity increasing from 

 group to group with the increase in molecular weight. 



The physiological resistance of saline plants to the action of sea salt, 

 A. Casu (Ann. But. [Home], 5 (1907), No. 2, pp. 273-35',, fujs. 2).—X study was 

 made of the flora of Cagliari to ascertain some of the fac-tors which determine the 

 distriiiution of plants in soils that are more or less impregnated with salt. After 

 an extended review of literature, the author gives in detail the results of his 

 investigation on the physical, chemical, and physiological effect of various salts 

 on the germination and growth of the strand flora, comparing the results 

 obtained in his experiments with the spontaneous occurrence of plants in the 

 regions studied. 



Observations on the effects of the rays of radium on plants, C. S. Gageb 

 (-U>,s-. in Science, n. ser., 25 (1907), No. ()3S, p. J,()2). — It has been shown that 

 the rays of radium and other radioactive substances act as a stimulus to germi- 

 nation and growth, and further experiments by the author warrant a similar 

 conclusion with respect to other plant activities, such as resjnration, starch 



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