METHODS OF INVESTIGATING GEOTROPISM 



169 



a little water the seedlings are kept moist, and to ensure an even distribution of 

 moisture wet blotting-paper may be placed around the inside of the cylinder. 



If the box (fi) is closed and a wood or cork plate attached to one of the axes, 

 a pot may be placed on it and rotated around a vertical axis, or the cover (3) may be 

 inclined at various angles and fixed by the screw-clamp () so that by means of the 

 gimbal attachment the rod (c) is able to rotate around an oblique akis. A pulley- 

 wheel can also be attached instead of the rod (c), and by means of a cord a glass 

 plate may be rotated under water l . The apparatus is strong enough to rotate several 



FlG. 36. Pfeffer's klinostat : A, showing mode of use with a potted plant ; B, with a cylinder 



containing seedlings. 



pots at the same time if they are properly attached 2 , and provided that the system is 

 equilibrated by means of the adjustable weight (e) so that the same amount of work 

 is performed at each phase of rotation. Finally, the time of a rotation may be varied 

 from two minutes to as long as eight hours. 



Fitting has recently constructed a special attachment which enables the plant to 

 be turned through an angle of 180 at a given time, or through a lesser angle. In 

 this way the side turned towards the light or to the ground may be suddenly placed 

 in the opposite position and the reversal repeated at regular intervals of time 3 . 



The various klinostats constructed by different authors do not appear to surpass 



1 Cf. Richter, Flora, 1894, p. 409; Klemm, Flora, 1893, p. 476. For transmission a thick 

 circular rubber tube is best. 



2 See A. Fischer, Bot. Ztg., 1890, p. 705. 



:1 A simpler intermittent klinostat was used by F. Darwin (Annals of Botany, 1892, Vol. VI, 

 p. 245). An intermittent electro-magnetic arrangement is easily made, and full details as to the 

 mode of use in such cases are given by Pfeffer in the Jahrb. f. wiss. Bot., 1900, Bd. xxxv, p. 738. 



