Botany; Geotropism; Plants -- Irritability and movements
Trifolium resupinatum.—A plant left entirely free was placed before a
north-east window, in such a position that a terminal leaflet projected
at right angles to the source of the light, the sky being uniformly
clouded all day. The movements of this leaflet were traced during two
days, and on both were closely similar. Those executed on the second
day are shown in Fig. 143. The obliquity of the several lines is due
partly to the manner in which the leaflet was viewed, and partly to its
having moved a little towards the light. From 7.50 A.M. to 8.40 A.M.
the leaflet fell, that is, the awakening movement was continued. It
then rose and moved a little laterally towards the light. At 12.30 it
retrograded, and at 2.30 resumed its original course, having thus
completed a small ellipse during the middle of the day. In the evening
it rose rapidly, and by 8 A.M. on the following morning had returned to
exactly the same spot as on the previous morning. The line representing
the nocturnal course ought to be extended much higher up, and is here
abbreviated into a short,
curved, broken line. The terminal leaflet, therefore, of this species
described during the daytime only a single additional ellipse, instead
of two additional ones, as in the case of T. subterraneum. But we
should remember that it was shown in the fourth chapter that the stem
circumnutates, as no doubt does the main petiole and the sub-petioles;
so that the movement represented in Fig. 143 is a compounded one. We
tried to observe the movements of a leaf kept during the day in
darkness, but it began to go to sleep after 2 h. 15 m., and this was
well pronounced after 4 h. 30 m.
Fig 143. Trifolium resupinatum: circumnutation and nyctitropic
movements of the terminal leaflet during 24 hours.
Trifolium repens.—A stem was secured close to the base of a moderately
old leaf, and the movement of the terminal leaflet was observed during
two days. This case is interesting solely from the simplicity of the
movements, in contrast with those of the two preceding species. On the
first day the leaflet fell between 8 A.M. and 3 P.M., and on the second
between 7 A.M. and 1 P.M. On both days the descending course was
somewhat zigzag, and this evidently represents the circumnutating
movement of the two previous species during the middle of the day.
After 1 P.M., Oct. 1st (Fig. 144), the leaflet began to rise, but the
movement was slow on both days, both before and after this hour, until
4 P.M. The rapid evening and nocturnal rise then commenced. Thus in
this species the course during 24 h. consists of a single great
ellipse; in T. resupinatum of two ellipses, one of which includes the
nocturnal movement and is much elongated; and in T. subterraneum of
three ellipses, of which the nocturnal one is likewise of great length.
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