Igt0] CROCKER, KNIGHT, ROBERTS—PEG OF CUCURBITS 337 
It must be remembered that while this experiment does not prove 
that gravity is not a direct stimulus in determining the size and 
lateral placement of the peg, it certainly furnishes no evidence 
that it is. 
A detailed statement of the results of one experiment with Big 
Tom on a centrifuge with a horizontal axis will suffice to indicate 
the nature of the results obtained with that apparatus. Here, 
also, the coats were removed at the tip and the temperature kept 
at 23°C. by means of a spray. The revolutions were 440 per 
minute and the circles 3 and 6 inches in diameter. The 3-inch 
circle gives 8.25 gravities, while the 6-inch gives 16.5. In the 
3-inch circle 15 were essentially pegless and 2 with slight two- 
sided pegs. In the 6-inch circle 25 were essentially pegless, 4 
with slight two-sided pegs, and one with a peg toward one edge 
of the seed. The marked tendency to show pegless forms is 
manifested here, as in all experiments on the centrifuge, with three 
or more gravities. It seems that these accelerations prevent all 
disposition to arching and to arching nutations; hence they give 
many pegless forms. 
OBLIQUE CLINOSTAT CULTURES 
A number of cultures were made on the oblique clinostat as 
devised by Frrtmnc.” The cultures.were watered by a spray at 
23° C. and grown with coats removed at the tip to avoid contact. . 
The end of the clinostat axis to which the frame for bearing the 
seeds was attached was pointed upward from the horizontal, while 
the radicles of the seeds pointed toward the axis. This insures, as an 
understanding of the oblique clinostat will show, that extreme arch- 
ing isavoided. The axis was placed at various angles with the hori- 
zontal, and the large plane of the seeds at corresponding angles 
with the axis. When the axis varied 5° from the horizontal, and 
the large plane of the seed was broken 5° from the axis, at one 
point in each revolution one flat face of the seed was exposed to 
gravity at an angle of 80° from the vertical (radicle pointing down- 
ward) and the other face at go°. As soon as considerable growth 
Occurs, of course geotropic response occurs in favor of the go” 
exposure, and this throws the flank of 80° exposure more nearly 
* See footnote 7. 
