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20. Vicia faba: circumnutation of a radicle, at first pointing
vertically upwards, kept in darkness, traced on a horizontal glass, during
14 hours. Movement of bead of filament magnified 23 times, here reduced to
one-half of original scale.
morning, the bead moved to a great distance in a nearly straight line, in
the direction indicated by the broken line in the figure. This resulted
from the tip bending quickly downwards, as it had now become much declined,
and had thus gained a position highly favourable for the action of
geotropism.
Fig. 21. Vicia faba: tracks left on inclined smoked glass-plates, by tips
of radicles in growing downwards. Plate C was inclined at 63o, plates A and
D at 71o, plate B at 75o, and plate E at a few degrees beneath the horizon.
[page 31]
We next experimented on nearly a score of radicles by allowing them to grow
downwards over inclined plates of smoked glass, in exactly the same manner
as with Aesculus and Phaseolus. Some of the plates were inclined only a few
degrees beneath the horizon, but most of them between 60o and 75o.


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