309 



and N, the distance of J from N must also vary In two obvious directions. 

 This is done by the screw O (Figs. 3 and 4), which holds the support of 

 the shaft carrying L. The shaft carrying the disk is enclosed for the 

 sake of lirniness in a sheath J. It is fastened to a disk of iron P. (Figs. 

 3 and 4), and this is held to the wooden disk of pine L. which is 20 cm. 

 in diameter and 2 cm. thick, by means of screws. Larger disks of wood 

 can, by means of these screws, be substituted for L and therefore the 

 centrifugal force considerably increased aside from the ways of increas- 

 ing the speed by the cone-pulley and bn-el-gear arrangement above re- 

 ferred to. The centrifugal force brought to bear on the objects under 

 investigation may also be increased by being placed near the periphery of 

 the disk L, or decreased by moving them nearer the center of L. The disk 

 of wood must in all cases be first boiled thoroughly in paratftne to pre- 

 vent swelling. The disk of wood L is covered by a circular sheet of 

 cork Q. This serves for the attachment of seedlings and plant parts to 

 be centrifuged, and to it also are fastened several layers of wet filter 

 paper for keeping the seeds moist. A glass crystallizing disk R, which will 

 exactly fit L. is placed over it and darkened by being painted thickly on 

 the inside with black paint. R is held to L liy clamps. In order to water 

 the seedlings when the machine is run for a long time, a hole is boi'ed 

 exactly in the center of the crystallizing disk R as at S. and even while 

 the disk is revolving Avater may be forced in against the filter paper on 

 the sheet of cork Q, and in this way be carried by absorption to all the 

 seeds on the disk Q. Fig. 3 shows the disk ready to rotate in a hori- 

 zontal direction. Fig. 4 shows the end view of the frame at A and 



Fi-. 4. 



indicates how the disk may be rotated not only horizontally but vertically 

 as well, or at any angle between the two by changing the position of the 

 shaft in J by loosening and moving the clamp at T. This machine is 

 also strong enough to carry any small flower pots with growing seedlings, 



