On the fourth day from the time of first attachment
the tip was bent towards the splinter.]
From these experiments it is clear that the apex of the radicle of the bean
is sensitive to contact, and that it causes the upper part to bend away
from the touching object. But before giving a summary of the results, it
will be convenient briefly to give a few other observations. Bits of very
thin glass and little squares
[page 141]
of common card were affixed with thick gum-water to the tips of the
radicles of seven beans, as a preliminary trial. Six of these were plainly
acted on, and in two cases the radicles became coiled up into complete
loops. One radicle was curved into a semi-circle in so short a period as 6
h. 10 m. The seventh radicle which was not affected was apparently sickly,
as it became brown on the following day; so that it formed no real
exception. Some of these trials were made in the early spring during cold
weather in a sitting-room, and others in a greenhouse, but the temperature
was not recorded. These six striking cases almost convinced us that the
apex was sensitive, but of course we determined to make many more trials.
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