454 PHYSIOLOGY OF GROWTH. 



320 marks from Albrecht, Tubingen (see Appendix). The high 

 price of the instrument 3 induced Wortmann to have clinostats 

 constructed in a much cheaper form (200 marks) by lingerer 

 Bros., Strassburg. 4 This Wortmann's instrument I have fre- 

 quently employed, and can recommend. It is certainly not so 

 good as the large apparatus of Pfeifer, but may be employed in 

 most cases. The following is a description of it : 



The whole clinostat, as represented in Fig. 148, consists of two 

 parts, a driving mechanism and the attachments, which latter 

 are essentially of the construction described by Pfeffer. The 

 driving mechanism, A, is screwed on to a strong stand, B, and 

 consists firstly of a clockwork, which is regulated not by an 

 anchor [lever], but, in order to secure perfectly smooth rotation, 

 by a fan [shown in Fig. 149] ; and secondly, of three spindles, 

 a, 6, and c, standing vertically over one another, which, them- 

 selves freely movable, can by means of a push knob, d, be put in 

 gear with a wheel of the clockwork, as shortly to be described, 

 and thereby set in rotation. The arbor, e, receives the key for 

 winding up the clockwork. 



The attachments consist firstly of a solid shaft, /, which, by 

 means of a joint, g, can be attached to any one of the spindles 

 a, 6, c. This joint enables the shaft f to be moved either in 

 a horizontal or vertical direction, and so, without disarranging 

 the whole apparatus, we can on the one hand rotate the research 

 objects with the axis of rotation horizontal or inclined at any 

 desired angle up to 45 with the horizontal, and on the other hand 

 secure different positions with respect to the incident rays of 

 light. On the shaft / is fixed by means of a set screw a movable 

 ring, carrying a pin, h, on which slides the weight i. The pin 

 and weight constitute a centering arrangement ; they provide a 

 means of counterbalancing any overweight, on one side or other 

 of the axis, of the objects under rotation, which might seriously 

 interfere with the regularity of the movement. The shaft / is 

 supported at a on two friction rollers, which are capable of 

 movement in a vertical direction upwards and downwards on 

 the pillar, fc, of a firm stand, and also capable of rotation round 

 the horizontal axis, /?, so as to accommodate the shaft / when 

 it is inclined to the horizontal. 



To the end of the shaft / is attached the flower-pot holder I. 

 This consists of a three-limbed brass base, into the segments of 

 which are rivetted at right angles three iron rods. Each of these 



