which was only .07 inch in length, stood almost vertically
[page 39]
upwards, in which position geotropism would act at first with little power.
A filament was attached near to its base, and projected at about an angle
of 45o above the horizon. The general course followed during the 11 hours
of observation and during the following night is shown in the accompanying
diagram (Fig. 26), and was plainly due to geotropism; but it was also clear
that the radicle circumnutated. By the next morning the tip had curved so
much downwards that the filament, instead of projecting at 45o above the
horizon, was nearly horizontal. Another germinating seed was turned upside
down and covered with damp sand; and a filament was fastened to the radicle
so as to project at an angle of about 50o above the horizon; this radicle
was .35 of an inch in length and a little curved. The course pursued was
mainly governed, as in the last case, by geotropism, but the line traced
during 12 hours and magnified as before was more strongly zigzag, again
showing circumnutation.

Four radicles were allowed to grow downwards over plates of smoked glass,
inclined at 70o to the horizon, under the

Fig. 27. Cucurbita ovifera: tracks left by tips of radicles in growing
downwards over smoked glass-plates, inclined at 70o to the horizon.

Fig. 28. Cucurbita ovifera: circumnutation of arched hypocotyl at a very
early age, traced in darkness on a horizontal glass, from 8 A.M. to 10.20
A.M. on the following day. The movement of the bead magnified 20 times,
here reduced to one-half of original scale.

same conditions as in the cases of Aesculus, Phaseolus, and Vicia.
Facsimiles are here given (Fig. 27) of two of these tracks; and a third