486 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the low temperature ; the two being in inverse proportion to one another. 

 The leaves of Alpine plants exhibit, as a rule, but very slight helio- 

 tropism. In this and in other respects the relationship of Arctic plants 

 to light differs materially from that of Alpine jdants. 



Biology of Creeping Plants.* — M. A. Maige has made a study of 

 the structure and properties of those plants which present creeping 

 stems, whether aerial or subterranean. The creeping habit of a branch 

 is always due to a form of geotropism which may be termed transverse. 

 These branches possess either positive or negative heliotropism, and a 

 geo-epinasty which determines a more or less considerable convexity of the 

 branch. When an erect becomes transformed into a creeping branch, it 

 passes through a series of oblique positions, each of which corresponds to 

 an oblique geotropic sensitiveness. Direct light produces on some species 

 darkness, on others a variation in the geotropic sensitiveness of obliquely 

 or transversely geotropic branches, and a return to a geotropism more 

 nearly allied to negative. Diffused light may transform the negative 

 geotropism of creeping branches into transverse. The first internodes 

 of creeping branches display a rapid intercalary growth, giving a cha- 

 racteristic appearance to the terminal bud. The nodes are furnished 

 with adventitious roots, and the power of producing these roots has 

 become hereditary. 



Carbon-dioxide Assimilation and Chlorophyll.f — Herr F. Czapek 

 gives a useful resume of recent literature on this subject, which shows 

 that the assimilation of carbon dioxide by chloroplasts in the light is 

 not dependent alone either on the action of thcTchlorophyll pigment, or 

 on the activity of the colourless protoplasmic stroma of the chlorophyll 

 grain. 



Influence of Copper Salts on Plants.* — Experiments made by MM. 



E. Chnard and F. Porchet tend to show that the favourable effects of 

 compounds of copper (Bordeaux mixture) on the growth and fertility of 

 plants have been exaggerated. The increase in the amount of sugar in 

 the fruit (grapes, gooseberries) never exceeded from 1 to 2 per cent. 

 Copper was never found in the leaves. The deeper colour of the leaves 

 is not due, they assert, to an increase in the amount of chlorophyll. 



Action of Leguminous Root-nodules in Water Cultures. § — Herren 



F. Nobbe and L. Hiltner find that the root-nodules of leguminous 

 plants (Ilobinia pseudacacia} are of little use to the plant when growing 

 in water. The structure of the nodules is altered, and they are filled 

 with water instead of air. When kept under water, they increase but 

 very little in size. 



Transpiration from Leaves which live more than one year.|| — 

 Herr 0. Rosenberg records the results of observations on the amount of 

 transpiration in those woody plants the leaves of which live more than 

 one year. He states that the stomates of last year's leaves are still 

 not closed for some time after the transpiration from this year's leaves 



* Ann. Sci. Nat. (Bot), xi. (1900) pp. 249-365 (4 pis. and 21 figs.). 

 + Bot. Ztg., lviii. (1900) 2 ,e Abt., pp. 05-70. 

 \ Bull. Soc. Vaudoise Sci. Nat., xxxfi. (1900) pp. 71-7. 



§ Landwirth. Vers.-Stat., lii. (1899) pp. 455-65. See Journ. Cheni. Soc, 1900, 

 Alistr. ii. p. 234. 



II Ofv. k. Vetensk. Akad. Forliandl. Stockholm, lvii. (1900) pp. S5-98 (German). 



