during the whole of the
[page 12]
2nd in the same general direction, and in a similar zigzag manner. From the
radicle not being quite perpendicular when the filament was affixed
geotropism came into play at once; but the irregular zigzag course shows
that there was growth (probably preceded by turgescence), sometimes on one
and sometimes on another side. Occasionally the bead remained stationary
for about an hour, and then probably growth occurred on the side opposite
to that which caused the geotropic curvature. In the case previously
described the basal part of the very short radicle from being turned
vertically upwards, was at first very little affected by geotropism.
Filaments were affixed in two other instances to rather longer radicles
protruding obliquely from seeds which had been turned upside down; and in
these cases the lines traced on the horizontal glasses were only slightly
zigzag, and the movement was always in the same general direction, through
the action of geotropism. All these observations are liable to several
causes of error, but we believe, from what will hereafter be shown with
respect to the movements of the radicles of other plants, that they may be
largely trusted.

Hypocotyl.--The hypocotyl protrudes through the seed-coats as a rectangular
projection, which grows rapidly into an arch like the letter U turned
upside down; the cotyledons being still enclosed within the seed. In
whatever position the seed may be embedded in the earth or otherwise fixed,
both legs of the arch bend upwards through apogeotropism, and thus rise
vertically above the ground. As soon as this has taken place, or even
earlier, the inner or concave surface of the arch grows more quickly than
the upper or convex surface; and this tends to separate the two legs and
aids in drawing the cotyledons out of the buried seed-coats. By the growth
of the whole arch the cotyledons are ultimately dragged from beneath the