94 The Botanical Gazette. [March, 
core-bearing end, to serve as a track for the small wooden 
wheels 7. The shaft extends four and one half inches beyond 
the wheel bearings. Four pulleys, 4, /, m, ”, are fastened to 
the shaft in the manner already described (p. 91); the three 
smaller pulleys having been trued up on the lathe after being 
fastened to the shaft, and the large pulley, which is cut out 
on the scroll saw, being screwed to these. The pulleys /, & 
which change the direction of the belt of the motor, can be 
adjusted along the plate ¢ as desired. A zinc case, eighteen 
inches in diameter and eight inches deep, painted black on 
the inside, stands on the shelf o. A hole in the back of the 
case one and three-fourths inches in diameter permits the 
free end of the shaft to pass into the case. A narrow sleeve 
soldered to the opening shuts out the light. A light copper 
wire wheel /, twelve inches in diameter, is crowded upon the 
shaft and revolves with it inside the case. The case is watet 
tight up to three inches from the bottom, and above this the 
whole of the front of the case is occupied by a door hinged 
at the base. Holes three-fourths inch in diameter and two 
inches apart are cut in the door in a circle of fourteen inches — 
diameter. These holes may be opened and closed by a zine 
strip placed behind them with corresponding holes, and oper 
ated by a knob. j 
Seedlings which have previously begun to germinate 1” 
moist white pine sawdust are fastened with two pins to large 
corks on the circumference of the wheel . The seedlings 
are kept moist by passing through the water in the bottom of 
the case during a short period of their revolution. : 
With this apparatus the influence of light on the direction 
of growth of the stems and roots of seedlings may be studied 
with the influence of gravity eliminated. 
When larger plants growing in pots are to be experimented 
with, the case and wire wheel are removed, and a zinc pan 15 
put on the shaft. If it is desired to place a single plant with 
its long axis horizontal the pan shown in plate XI, fig. 38 
used. This is ten inches in diameter and eight inches deep. 
The tube g, soldered to the base of the pan and made rigid 
by brackets, fits over the shaft £4 and is held in position by 4 
screw. The flower pot is imbedded in the pan in moist saw~ 
dust, and after fine excelsior has been placed over the saw~ 
dust and front of the pot the whole is bound in with a string 
passing over hooks soldered to the side of the pan. If sev~ 
