From the several foregoing facts, there can be no doubt that the
cauterisation of the tip of the radicle of this Cucurbita on one side, if
done lightly enough, causes the whole growing part to bend to the opposite
side.
Raphanus sativus: Sensitiveness of the apex of the Radicle.--We here
encountered many difficulties in our trials, both with squares of card and
with caustic; for when seeds were pinned to a cork-lid, many of the
radicles, to which nothing had been done, grew irregularly, often curving
upwards, as if attracted by the damp surface above; and when they were
immersed in water they likewise often grew irregularly. We did not
therefore dare to trust our experiments with attached squares of card;
nevertheless some of them seemed to indicate that the tips were sensitive
to contact. Our trials with caustic generally failed from the difficulty of
not injuring too greatly the extremely fine tips. Out of 7 radicles thus
tried, one became bowed after 22 h. at an angle of 60o, a second at 40o,
[page 172]
and a third very slightly from the perpendicular and from the cauterised
side.
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