Botany; Geotropism; Plants -- Irritability and movements
(12.) Echeveria stolonifera (Crassulaceæ, Fam. 84).—The older leaves of
this plant are so thick and fleshy, and the young ones so short and
broad, that it seemed very improbable that any circumnutation could be
detected. A filament was fixed to a young upwardly inclined leaf, .75
inch in length and .28 in breadth, which stood on the outside of a
terminal rosette of leaves, produced by a plant growing very
vigorously. Its movement was traced during 3 days, as here shown (Fig.
104). The course was chiefly in an upward direction, and this may be
attributed to the elongation of the leaf through growth; but we see
that the lines are strongly zigzag, and that occasionally there was
distinct circumnutation, though on a very small scale.
Fig. 104. Echeveria stolonifera: circumnutation of leaf, traced from
8.20 A.M. June 25th to 8.45 A.M. 28th. Apex of leaf 12 1/4 inches from
the glass, so that the movement was much magnified; temp. 23°–24½° C.
(13.) Bryophyllum (vel Calanchæ) calycinum (Crassulaceæ).—Duval-Jouve
(‘Bull. Soc. Bot. de France,’ Feb. 14th, 1868) measured the distance
between the tips of the upper pair of leaves on this plant, with the
result shown in the following Table. It should be noted that the
measurements on Dec. 2nd were made on a different pair of leaves:—
8 A.M. 2 P.M. 7 P.M. Nov. 16. . . . . . . . . . . . . . . . .
. .15 mm.. . . . . .25 mm. . . .. . . .(?) ” 19. . . . . . . . . .
. . . . . . . . .48 ” . . . . . . . 60 ”. . . . . . . 48 mm. Dec.
2. . . . . . . . . . . . . . . . . . .22 ”. . . . . . . . 43 ”. . . .
. . . .28 ”
We see from this Table that the leaves stood considerably further apart
at 2 P.M. than at either 8 A.M. or 7 P.M.; and this shows that they
rise a little in the evening and fall or open in the forenoon.
(14.) Drosera rotundifolia (Droseraceae, Fam. 85).—The movements of a
young leaf, having a long petiole but with its tentacles (or
gland-bearing hairs) as yet unfolded, were traced during 47 h. 15 m.
The figure (Fig. 105) shows that it circumnutated largely, chiefly in a
vertical direction, making two ellipses each
day. On both days the leaf began to descend after 12 or 1 o’clock, and
continued to do so all night, though to a very unequal distance on the
two occasions. We therefore thought that the movement was periodic; but
on observing three other leaves during several successive days and
nights, we found this to be an error; and the case is given merely as a
caution. On the third morning the above leaf occupied almost exactly
the same position as on the first morning; and the tentacles by this
time had unfolded sufficiently to project at right angles to the blade
or disc.
Fig. 105. Drosera rotundifolia: circumnutation of young leaf, with
filament fixed to back of blade, traced from 9.15 A.M. June 7th to 8.30
A.M. June 9th. Figure here reduced to one-half original scale.
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Elsewhere in the archive
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account