464 PHYSIOLOGY OF GROWTH. 



Two short test-tubes, about 55 mm. long and 25 mm. wide, are 

 filled with moist sawdust. In this we lay a few seeds of Lepidium 

 sativum. In the dark they rapidly begin to germinate, and 

 when the hypocotyls, with their ends nodding, have emerged from 

 the sawdust, the experiment can begin. To fasten the culture 

 cylinders diametrically opposite one another, at the periphery of 

 the cork, we slip them into pieces of cork perforated in the 

 middle, and attach these by means of several pins to the large 

 cork plate of the apparatus. After some hours the result of the 

 experiment is clearly to be made out. The hypocotyls, directed 

 at the beginning of the experiment parallel with the horizontal 

 axis of rotation, have experienced a fresh curvature somewhat 

 below the place at which they are curved owing to spontaneous 

 nutation. The parts of the hypocotyl lying above this new zone 

 of curvature have directed themselves towards the centre of the 

 disc, not like the growing root tips towards the periphery of the 

 disc. Seedlings of Triticum are also suitable objects for investiga- 

 tion. 



I have now designed a large centrifugal apparatus (to be 

 obtained for 70 marks from G. Tegetmeier, mechanician at the 

 Physical Institute at Jena), by means of which, e.g., even large 

 flower-pots, with soil and plants growing in them, can be sub- 

 mitted to rapid rotation (e.g. 300 revolutions per minute), and 

 which serves very well for thoroughly investigating the in- 

 fluence of centrifugal force, on plants. I have indeed already 

 made many experiments with this arrangement. 



In Fig. 155 the apparatus is represented as arranged for rotation 

 about a vertical axis. 



On the stout board H is screwed a metal bracket, M. Along- 

 side this is the support Ah for the shaft, which can be fixed 

 rigidly to M by means of the set screw Sch and the pin St 

 when the axis of rotation is required to be vertical. The shaft 

 has a length of 20 cm. At a it rests on a pivot not visible in 

 the drawing ; at b is a bearing for the shaft. Over the grooved 

 disc, c, which is attached to the shaft, can be passed an endless 

 cord. The shaft support is perforated at d. In the perforation 

 is inserted the lower end of the metal tube, Mr, which has a very 

 fine opening. Into this tube we pour a little oil to ensure adequate 

 lubrication of the bearing at high rates of revolution. Oil is also 

 applied at intervals to the end a of the shaft. If the apparatus 

 has not been in use for some time, it must be freed at a and b 



