80 THE AMERICAN NATURALIST. | [Vor. XXXIX. 
deviation in question than in the other, it was proposed to 
incline the plants first 9o degrees from the normal vertical posi- 
tion, then r35 degrees from the normal, but in the opposite 
direction, and to alternate between these two positions giving 
the same length of time and number of exposures in each, until 
a decided curve should result. 
A special frame, devised by Professor Newcombe, made it 
possible to experiment with a considerable number of potted 
plants at one time. This frame was furnished with a hinged 
rack for holding the pots and this was so hung or supported . 
that by turning it from one stop to another, through an arc of 
225 degrees, the plants could be set first at an angle of 9o 
degrees, on one side of the vertical position, then at an angle of 
135 degrees on the opposite side, or vice versa, and could be 
quickly and easily turned from one position to the other with a 
minimum of jarring. 
The stems of the young plants selected were first tied to 
upright sticks or wires, leaving the upper, growing portions of 
the axes free to curve, while the weight of the older parts of the 
stems was supported to prevent all sagging when they were 
turned out of their normal position. In the case of several 
seedlings in one pot, all whose hypocotyls were not vertical were 
cut away at the outset. The pots were then firmly wedged in 
the frame, care being taken to keep the growing tips upright. 
When all was in readiness, the frame and its rack were turned 
so as to bring all the stems into one of the two positions 
desired, and alternation was begun. 
Experimentation. 
Young plants of Chrysanthemum, Ageratum, Lavandula, 
Fuchsia, Heliotropium, and Coleus were used in these experi- 
ments; also seedlings of Linum usitatissimum, Raphanus sativus, 
Brassica alba, and Helianthus annuus. The process of alterna- 
tion was continued from 2 to 73 hours according to the sensitive- 
ness of the plants. When a noticeable curve appeared after an 
equal number of exposures in the two positions, the pots were 
set upright again and the direction of the stems was carefully 
noted. 
