260 BOTANICAL GAZETTE | SEPTEMBER 
by means of a set screw to any position on the rod required, thus 
enabling one to modify the speed. i 
If, for example, the friction wheel be placed upon the shaft near 
the center of the disk, the speed is retarded; if, on the contrary, it is 
placed near the circumference, then the speed is accelerated. When 
the friction wheel is 23"" from the center of the disk, the small shalt 
revolves once every half hour, at a distance of 46™" from the centerit 
revolves every fifteen minutes, and when at 69™™" it revolves im seven 
and one-half minutes. In fact any degree of speed can be obtained 
between seven and one-half and thirty minutes. Should it be neces 
sary to obtain a higher speed a smaller friction wheel can be used, of 
the hair spring can be shortened still further. /%g. 2 shows a side view 
of the clinostat when set up for the purpose of eliminating the effects 
of light, the plants being placed upon the horizontal disk (d). In 
figs. 7, 3, 4, and 5 the instrument is shown when in use for gravity 
experiments. In the latter instance the steel rod is placed horizontally. 
The apparatus is so arranged that any angle can be obtained. ‘This 's 
accomplished by means of three set screws (e) which are attached to the 
clock and fit into depressions in the metal rim (7) which is movable. 
This mechanism is shown more in detail in the enlarged cross-section 
of fig. 5, the metal rim being represented by the shaded portion. By 
loosening the three set screws (e) the rim can be revolved, and as the shaft 
attachments are connected with the rim they move with it. In fig-1# 
holder is attached to the end of the shaft for the purpose of carrying 
the plant. The pot used is 2" in diameter, and is centered and held 
in place by means of three screws. A simpler method of holding the 
plant is shown in fig. 6, where the end of the shaft is made t ar 
is only necessary to remove the friction wheel from the disk at 
allows the shaft to revolve freely, then adjust the compensating pee 
(4), bringing the center of gravity of the pot within that of tHe wei 
Instead of using a growing plant in the pot, grass nodes, OT get 
stalks, can be readily substituted. For eliminating the effect of ee 
in roots the apparatus is set up as shown in fg. 2, in wi 
roots are kept from drying up by revolving in a dish of wae 
For Phycomyces or Mucor it can be conveniently arranged ene 
fig. 4, in which case the shaft is elongated. The clinostat is moun 
