1990 BOTANICAL GAZETTE [MARCH 
depressed growth of nos. 2 and 7 is correlative with the imbed- 
ding, as wellas due to the wound. Removing the plumule does 
not hinder the elongation of the hypocotyl. When the split 
was horizontal the halves became bowed apart, and the angle of 
curvature given is the least at which they could be brought into 
continuous contact. 
The first notion suggested by the excessive curvature of the 
hypocotyls with horizontal split surface is that they are respond- 
ing to a stimulus received by the imbedded part of the plant. But 
the facts that a half stem is known to be in itself irritable, and 
that the extreme curvature, 180°, occurred whether it was root 
or cotyledon that remained horizontal, point toward the conclu- 
sion that in the experiment each half of the split hypocotyl 
responds only to a stimulus received im Joco; and that a half 
hypocotyl has something in its own structure, independent of 
any comparison of conditions with the other half, which will 
make it grow more rapidly if the split is the upper than if it is 
the lower surface. 
Two plants were next split from the tops well into the roots, 
one having the cotyledons split, the other separated; both had 
the roots imbedded. The halves of one were too weak to 
become quite erect, but those of the other bent up side by side, 
and after they became erect the lower half slid along the upper 
so as to reach beyond it. In both cases the growth of the lower 
half exceeded that of the upper by 3™. The experiment was 
repeated, giving a little less difference. 
July 13, a number of plants were split from end to end, and 
the entirely separated halves imbedded side by side, some with 
the roots, others with the cotyledons free, all with the cut surface 
horizontal. The growth in forty-eight hours follows : 
: Growth of Growth of 
upper half lower half 
in mm in mm 
te ESE oak! ae Une ae, 3-5 
St en ae 2.0 3-5 
3- ' . . - ge 4.0 
: Cee ee es 5.0 
: * . : - a Ow 2.3 
hee is 
