500 W. Wendler: Physikalische Physiologie 1921— 1922 [34 



315. Embersi'er, L. Contribiition a Tetude cytologique du 

 sporange chez les Fougeres. (C K. Acad. Sei. Paris CLXXIII, 1921, 

 p. 1485—1487, 1 Abb.) — Kef. in Bot. Ctrbl., N. F. I, 1922, p. 386. 



316. Funke. G.-L. Sur les pousses siipplementaires estivales. 

 (C. E. Acad. 8ei. Paris CLXXV, 1922, p. 901—904.) — Eef. in Bot. Ctrbl., 

 N.F. 2, 1923, p. 356—357. 



317. Greu'ory, F. G. Studies in tlie energy relations of plants. 



I. Tlie increase in area of leaves and leaf surface oi Cucumis sativus. 



(Ann. of Bot. XXXV, 1921. p. 93—123, mit 15 Textfig.) — Summary: 



,,A metliod is described for ascertaining the areas of leaves without detaching 



tbem from tlie plant. The errors of the method are discussed, and it is showii 



that a Single determination of the total area of the leaf surface is significant 



to 5 per Cent. — The growth in length and breadth and in area of leaves 



in daylight is shown to follow the same law as the growth in length of axial 



Organs, displaying a grand ijeriod of growth. Under continuous electric liglit, 



however, thie rate of increase falls off from the first measurement of area 



onwards. — The curves of increase in area and in linear dimensions for a single 



leaf in daylight are of S form, and can be fairly represented by the formula 



of an autocatalytic reaction in whieh the material catalysed gradually decreases 



in amount as the reaction proceeds. A modification of this formula is intro- 



duced to represent tbe growth in area of single leaves under artificial light. — 



The increase in area of the total leaf surface of plants grown in daylight in 



Marcb and June closely follows a Compound interest law, the rate of increase 



at any time being proportional to the area existing at that time. For plants 



grown in December, however, the increase in total leaf area follows a more 



complex law, which may be represented by the f unction A = ae '^ '°s * = at "^ ; 



dA rA 

 tbe rate of increase at any time is then given by the equation ■— — = — , sbowing 



dt t 



that the rate of increase is still proportional to the leaf area already extant, 



but tends to fall off with time, owing to the action of a detrimental factor. 



In the case of plants grown under artificial light, the increase in total leaf 



area is found to follow the same law as for jjlants grown in füll daylight in 



December. and also shows the action of a detrimental time factor. It is suggested 



that the detrimental factor in this case may have been due to the high tempe- 



rature maintained during the experiment. — It is shown that under comparable 



conditions the average leaf area is determined by the product of intensity and 



duration of liglit radiation. — In Support of the Compound interest law of 



leaf -surface growth coefficients are quoted for correlations between: 1. maxi- 



mum area of cotyledons and maximum area of 1^* leaf: r = + 0.54; 2. maxi- 



mum area of cotyledons and dry weight of plants after 30 days: r = + 0.36; 



3. growth rate and crop weight: r = + 0.7." 



318. Janse, J. >I. Ein Blattsteckling von Camellia japonica mit 

 Adventivknospe. (Flora, N. F. XIV, 1921, p. 401—404. mit 1 Textabb.) — 

 Je 10 lederartige Blätter von Ficiis elastica, Auaiba japonica und Camellia 

 japonica wurden im März abgeschnitten und mit dem Stiele in feuchten Sand 

 gesteckt. Die Blätter blieben etwa 3 Jahre am Leben und hatten in dieser 

 Zeit Wurzeln bis 70 cm Länge mit nur wenigen Seitenwurzeln gebildet. Ein 

 Blatt von Camellia bildete etwa 21/0 Jahre nach dem Abtrennen des Blattes 

 in 3 cm Entfernung von der Blattstielbasis an der Wurzel eine Adventiv- 



