336 BOTANICAL GAZETTE [NOVEMBER 
cultures were grown in a spray at 23° C.; the coats were removed 
to avoid all contact; and the long axis of each seed was arranged 
parallel with a radius of the centrifuge, the radicle directed away 
from the axis. 
Three facts were noticeable in such seedlings, especially in those 
grown with the greater centrifugal acceleration: (1) the hypocotyls 
were very straight, (2) the pegs were smaller than in similar cul- 
tures on clinostat or with radicles pointing vertically downward, 
and (3) the pegs though small were approximately equal on all 
flanks. 
If, as NoLt assumes, gravity calls forth the peg in seedlings 
with the radicles pointing downward, one would expect larger 
pegs with increased gravities, unless the rather remarkable situa- 
tion exists that one gravity is the optimum or is greater than the 
optimum for peg-development. But how can one account for the 
more meager and very regular peg? This is undoubtedly due 
to all arch strains being overcome by the centrifuge, which removed 
this stimulus to the enlargement and unequal distribution of the 
g. 
It must not be forgotten that a centrifuge thus operated gives 
two mass accelerations at right angles to each other: one due to 
the centrifugal acceleration produced by the machine and acting 
in the direction of the pointing root, and one gravity downward. 
If a flat side of the seedling faces downward, and the machine 
gives a centrifugal acceleration of three gravities, three gravities 
act in the direction of the pointing root and one gravity downward. 
Such cultures showed very slight tendency to arch, and no greater 
peg-development on the lower than on the upper flank. If this 
organ were sensitive to gravity, one would expect it to show a 
greater response on the side where one extra gravity was ee 
especially when the centrifugal acceleration was only three gravites- 
Of course it is entirely possible that WEBER’s law applies in such 
proportions that the application of one gravity as a stimulus cate 
not be perceived when three gravities are acting at right angles 
to it. In geotropism of Vicia Faba epicotyls, however, a 
law applies in the proportion of 24-25, that is 4 per cent excess 
exposure to gravity in one direction is sufficient to give a respons® 
