462 



PHYSIOLOGY OF GROWTH. 



2 Sachs and Noll described the special behaviour of dorsiventral organs when 

 rotated on the clinostat (Flora, 1893). 



3 Albrecht also supplies a clinostat for 220 marks. 



4 See Wortmann, Berichte d. Deutsclien botan. Gesellscliaft, Bd. 4. 



5 See Sachs, Arbeiten des botan. Inst. in Wiirzburg, Bd. 2, p. 217 ; and Dietz, 

 Unters. a. d. botan. Inst. zu Tubingen, Bd. 2, p. 478. 



6 See Wortmann, Botan. Zeitung, 1887, No. 49. 



177. Experiments with the Centrifugal Apparatus. 



I will first describe a form of centrifugal apparatus designed 

 by myself, and depicted in Fig. 153, which can be very easily 

 and cheaply constructed, and which is very suitable for de- 

 monstration purposes. The most important part of the apparatus 

 is the brass shaft A, about 50 cm. in length, Avhich carries the 

 zinc disc, Z, 40 mm. in diameter, on which are soldered the six 

 metal vanes, 3 cm. wide and 7'5 cm. long. At the opposite end 



Zr 



FIG. 153. Centrifugal apparatus. 



of the axis is fixed a disc of wood, H, 140 mm. in diameter, to 

 which is attached a sheet of cork. The zinc ring, Zr, is fixed 

 to the margin of the disc of wood, but projects beyond it, and 

 may be employed to give support to a zinc cylinder about 11 cm. 

 in length, closed at one end, and serving as a cover, so that, e.g., 

 seedlings, fixed to the cork with pins, are excluded from the light 

 when the cover is put on. In the drawing the wooden disc, H, 

 carries a bell-glass, K. The shaft A rests at b in a bearing. 

 At c is a second point of support for the shaft, the end of which 

 here forms a point. As our drawing shows, the arrangement 

 described is supported by a box. This is about 15 cm. high, 27 



