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1910] | CROCKER, KNIGHT, ROBERTS—PEG OF CUCURBITS 339 
Eucalyptus and Cuphea, where it is an equal ring all around the 
organ; or its formation may begin after germination, when its 
position and size are determined by the factors we have shown to 
be effective. 
The lateral placement is apparently brought about by the 
arching of the hypocotyl. Two stimuli aid in the formation of 
the arch: contact of the coats and gravity. Contact of the coats 
is by far the more effective, for it will induce very sharp arching 
even against gravity. 
In forms like the Boston marrow, gravity independent of contact 
with a deviation of 170° from the vertical gives strong enough 
arching to produce only go per cent with one-sided pegs. In 
_ Big Tom and various other forms it is somewhat more effective. 
Arching leads to an increased development of the peg, as well 
as to its lateral placement, and in many cases it produces a peg 
where it would not otherwise appear, as in Big Tom. Contact 
likewise increases the size of the peg independent of its effect 
through arch-production. 
No evidence obtained from this detailed study indicates that 
gravity, as a direct stimulus, in the least increases the peg-develop- 
ment. 
Tue University or CHICAGO 
