1 89 1.] Anatomical and Physiological Researches. 343 



Noteworthy anatomical and physiological researches. 



■ 



CONWAY MAC MILLAN. 



Influence of gravity on sleep-movements. 1 



Fischer has attempted in these researches to discover the 

 influence of gravitation upon the positions assumed by nycti- 

 tropic organs during the changing diurnal and nocturnal con- 

 ditions. The method of experimentation adopted was simple. 

 Two groups of cultures were arranged, in one of which plants 

 were placed in abnormal inclinations to the plane of gravity- 

 stimulation, while in the other, the plants were rotated upon 

 the klinostat. By these means it was possible to. show that 

 the plants experimented upon could be grouped in two classes: 

 (1) those which continued the nyctitropic movements regard- 

 less of the direction from which the force of gravity acted; 

 and (2) those which failed to assume nyctitropic positions in 

 the absence of normal gravity-stimulus. The first group of 

 plants — to which belong Trifolium pratense, Portulaca sativa, 

 Cassia Marylandica, Oxalis lasiandra, Acacia lophantha and 

 others — is named by Fischer auto-nyctitropic. The second 

 group, apparently smaller than the first, includes Gossypium 

 arboreum, Phaseolus multiflorus, Lupinus aibus and 'certain 

 Malvaceae, and is named gco-nyctitropic. These experiments, 

 if extended, might be fruitful in explaining some difficult 

 problems in plant positions. It would seem particularly de- 

 sirable to determine, if possible, for a 'number of plants, the 

 critical angle at 



: which nyctitropic movements fail to appear. 



rhich might easily be investigated in many 



This is a line w .«**.«* «.. & 



American laboratories. 



Effects of transpiration and darkness on form. 2 



Wiesner here continues experimentation somewhat along 

 the line indicated by Palladin and others, with reference to 

 the connection between the form of a plant and its rate of 

 transpiration. He has examined more particularly those 

 plants which normally form a basal rosette of leaves, as in the 

 case of Taraxacum, Capsella, Sempervivum, etc. He finds that 



* A, Fischer : Ueberdeo Einfluss der Schwerkraft auf die Schlafbewegungen 



der Blaetter. Botanische Zeitung, 1890. *„,„-!,»«, 



* J. Wiesner : Formamderung von Pflanzen be, Culture ,m absolut fe uch ten 

 Raumer und im Dunkeln. Berichte der deutschen bot. Gesellsch., 1&91, p. 4 <> 



