Botany; Geotropism; Plants -- Irritability and movements
narrow ellipses, each completed in about 26 h. The following statement,
however, seems to indicate something different from ordinary
circumnutation, but we cannot fully understand it. M. Rodier says: “Il
est alors facile de voir que le mouvement de flexion se produit d’abord
dans les mérithalles supérieurs, qu’il se propage ensuite, en
s’amoindrissant du haut en bas; tandis qu’au contraire le movement de
redressement commence par la partie inférieur pour se terminer a la
partie supérieure qui, quelquefois, peu de temps avant de se relever
tout à fait, forme avec l’axe un angle très aigu.”
[1] ‘Comptes Rendus,’ April 30th, 1877. Also a second notice published
separately in Bourdeaux, Nov. 12th, 1877.
Fig. 82. Verbena melindres: circumnutation of stem in darkness, traced
on vertical glass, from 5.30 P.M. on June 5th to 11 A.M. June 7th.
Movement of bead magnified 9 times.
(18.) Coniferæ.—Dr. Maxwell Masters states (‘Journal Linn. Soc.,’ Dec.
2nd, 1879) that the leading shoots of many Coniferæ during the season
of their active growth exhibit very remarkable movements of revolving
nutation, that is, they circumnutate. We may feel sure that the lateral
shoots whilst growing would exhibit the same movement if carefully
observed.
(19.) Lilium auratum (Fam. Liliaceae).—The circumnutation of the stem
of a plant 24 inches in height is represented in the above figure (Fig.
83).
Fig. 83. Lilium auratum: circumnutation of a stem in darkness, traced
on a horizontal glass, from 8 A.M. on March 14th to 8.35 A.M. on 16th.
But it should be noted that our observations were interrupted between 6
P.M. on the 14th and 12.15 P.M. on the 15th, and the movements during
this interval of 18 h. 15 m. are represented by a long broken line.
Diagram reduced to half original scale.
Fig. 84. Cyperus alternifolius: circumnutation of stem, illuminated
from above, traced on horizontal glass, from 9.45 A.M. March 9th to 9
P.M. on 10th. The stem grew so rapidly whilst being observed, that it
was not possible to estimate how much its movements were magnified in
the tracing.
(20.) Cyperus alternifolius (Fam. Cyperaceae.)—A glass
filament, with a bead at the end, was fixed across the summit of a
young stem 10 inches in height, close beneath the crown of elongated
leaves. On March 8th, between 12.20 and 7.20 P.M. the stem described an
ellipse, open at one end. On the following day a new tracing was begun
(Fig. 84), which plainly shows that the stem completed three irregular
figures in the course of 35 h. 15 m.
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