Avena sativa.--The cotyledons of this plant become quickly bowed towards a
lateral light, exactly like those of Phalaris.
[page 478]
Experiments similar to the foregoing ones were tried, and we will give the
results as briefly as possible. They are somewhat less conclusive than in
the case of Phalaris, and this may possibly be accounted for by the
sensitive zone varying in extension, in a species so long cultivated and
variable as the common Oat. Cotyledons a little under three-quarters of an
inch in height were selected for trial: six had their summits protected
from light by tin-foil caps, .25 inch in depth, and two others by caps .3
inch in depth. Of these 8 cotyledons, five remained upright during 8 hours
of exposure, although their lower parts were fully exposed to the light all
the time; two were very slightly, and one considerably, bowed towards it.
Caps only .2 or .22 inch in depth were placed over 4 other cotyledons, and
now only one remained upright, one was slightly, and two considerably bowed
to the light. In this and the following cases all the free seedlings in the
same pots became greatly bowed to the light.
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