Botany; Geotropism; Plants -- Irritability and movements
The main petiole was now secured to a stick close to the base
of the two terminal leaflets, which were 1.4 inch in length; and the
movements of one of them were traced during 48 h. (see Fig. 101). The
course pursued is closely analogous to that of the whole leaf. The
zigzag line between 8.30 A.M. and 3.30 P.M. on the second day
represents 5 very small ellipses, with their longer axes differently
directed. From these observations it follows that both the whole leaf
and the terminal leaflets undergo a well-marked daily periodical
movement, rising in the evening and falling during the latter part of
the night or early morning; whilst in the middle of the day they
generally circumnutate round the same small space.
Fig 101. Vicia faba: circumnutation of one of the two terminal
leaflets, the main petiole having been secured, traced from 10.40 A.M.
July 4th to 10.30 A.M. 6th. Apex of leaflet 6 5/8 inches from the
vertical glass. Tracing here reduced to one-half of original scale.
Temp. 16°–18° C.
(10.) Acacia retinoides (Leguminosae).—The movement of a young
phyllode, 2 3/8 inches in length, and inclined at a considerable angle
above the horizon, was traced during 45 h. 30 m.; but in the figure
here given (Fig. 102), its circumnutation is shown during only 21 h. 30
m. During part of this time (viz., 14 h. 30 m.) the phyllode described
a figure representing 5 or 6 small ellipses. The actual amount of
movement in a vertical direction was .3 inch. The phyllode rose
considerably between 1.30 P.M. and 4 P.M., but there was no evidence on
either day of a regular periodic movement.
Fig. 102. Acacia retinoides: circumnutation of a young phyllode, traced
from 10.45 A.M. July 18th to 8.15 A.M. 19th. Apex of phyllode 9 inches
from the vertical glass; temp. 16½°–17½° C.
(11.) Lupinus speciosus (Leguminosae).—Plants were raised from seed
purchased under this name. This is one of the species in this large
genus, the leaves of which do not sleep at night. The petioles rise
direct from the ground, and are from 5 to 7 inches in length. A
filament was fixed to the midrib of one of the longer leaflets, and the
movement of the whole leaf was traced, as shown in Fig. 103. In the
course of 6 h. 30 m. the filament went four times up and three times
down. A new tracing was then begun (not here given), and during 12½ h.
the leaf moved eight times up and seven times down; so that it
described 7½ ellipses in this time, and this is an extraordinary rate
of movement. The summit of the petiole was then secured to a stick, and
the separate leaflets were found to be continually circumnutating.
Fig. 103. Lupinus speciosus: circumnutation of leaf, traced on vertical
glass, from 10.15 A.M. to 5.45 P.M.; i.e., during 6 h. 30 m.
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