186 BOTANICAL GAZETTE [MARCH 
plant has seemed to me worthy an experimental answer. Such 
a trace would appear as a sort of polarity, such that if the fixed 
point of the hypocotyl were moved upward from the base, only 
the upper free part would remain disposed to become erect. To 
answer this question I transferred the fixed point at once from 
base to apex, in each case leaving the other end free. The result 
was unequivocal, and as the data from several experiments were 
in all essentials alike, it will suffice if a single series is reported. 
The seeds were germinated on a net over water and the seed- 
lings selected were perfectly straight and as uniform as possible. 
The hypocotyls, 6-6.5°" long, were marked off into zones of 1™ 
each, and these zones were numbered from the cotyledons down- 
ward. The end to be fixed was imbedded in a block of gypsum 
plaster, and these blocks were placed, with the hypocotyl hori- 
zontal, in a closed glass vessel containing some water. The 
experiment was begun at I0 A.M., April 12, 1899, and at 4 P.M. 
the free ends were all directed upward at angles of 50-70, 
those having free cotyledons being somewhat more sharply ele- 
vated than those having free roots. They were left undisturbed 
for six days, at a lower temperature than Cucurbita likes, about 
18° C, in general, and were then removed and the growth and 
curvature measured. The curvature is expressed in the follow- 
ing table in figures representing the radius of the arc, measured 
by a Sachs’ cyclometer. Plants 2 and 4 had the roots imbedded ; 
plants 1 and 3 the cotyledons, so that zone I vas next the plaster. 
PLANT 1. 
Hypocoty! straight and erect (the roots in air) to within 6 of the cotyle- 
ons. The radius of the curve for the upper 5" of the hypocotyl and 
the exposed 5™™ of the cotyledons was about 1°™, 
I 
PLANT 2, = - : : 
Curvature (in Cm) 46 9 6 3 5 be 
Growth (in mm.) 3 3.5 2.7 2 
PLANT 3. 
Curvature (in cm.) 2 3 4 7 a: 
Growth (in mm.) 1.7 oe | 1.3 1 
PLANT 4. 
Curvature (in em.) 14 Io 4 3 4 ; 
Growth (in mm.) 4.5 2 1.7 I I 
