M. on 22nd. The movement of the bead of the filament
was at first magnified 21 times, or 10 1/2, in figure here given, and
afterwards 36 times, or 18 as here given; seedling illuminated from above.
Aesculus hippocastanum (Hippocastaneae).--Germinating seeds were placed in
a tin box, kept moist internally, with a sloping bank of damp argillaceous
sand, on which four smoked glass-plates rested, inclined at angles of 70o
and 65o with the horizon. The tips of the radicles were placed so as just
to touch the upper end of the glass-plates, and, as they grew downwards
they pressed lightly, owing to geotropism, on the smoked surfaces, and left
tracks of their course. In the middle part of each track the glass was
swept clean, but the margins were much blurred and irregular. Copies of two
of these tracks (all four being nearly alike) were made on tracing paper
placed over the glass-plates after they had been varnished; and they are as
exact as possible considering the nature of the margins (Fig. 18). They
suffice to show that there was some lateral, almost serpentine movement,
and that the tips in their downward course pressed with unequal force on
the plates, as
[page 29]
the tracks varied in breadth.
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