The Life and Letters of Darwin, Volume 2
The 'Power Of Movement In Plants'
[The few sentences in the autobiographical chapter give with sufficient clearness the
connection between the 'Power of Movement,' and one of the author's earlier books, that
on 'Climbing Plants.' The central idea of the book is that the movements of plants in
relation to light, gravitation, etc., are modifications of a spontaneous tendency to revolve
or circumnutate, which is widely inherent in the growing parts of plants. This conception
has not been generally adopted, and has not taken a place among the canons of orthodox
physiology. The book has been treated by Professor Sachs with a few words of
professorial contempt; and by Professor Wiesner it has been honoured by careful and
generously expressed criticism.
Mr. Thiselton Dyer ('Charles Darwin' ('Nature' Series), page 41.) has well said: "Whether
this masterly conception of the unity of what has hitherto seemed a chaos of unrelated
phenomena will be sustained, time alone will show. But no one can doubt the importance
of what Mr. Darwin has done, in showing that for the future the phenomena of plant
movement can and indeed must be studied from a single point of view."
The work was begun in the summer of 1877, after the publication of 'Different Forms of
Flowers,' and by the autumn his enthusiasm for the subject was thoroughly established,
and he wrote to Mr. Dyer: "I am all on fire at the work." At this time he was studying the
movements of cotyledons, in which the sleep of plants is to be observed in its simplest
form; in the following spring he was trying to discover what useful purpose these sleep-
movements could serve, and wrote to Sir Joseph Hooker (March 25th, 1878):--
"I think we have PROVED that the sleep of plants is to lessen the injury to the leaves
from radiation. This has interested me much, and has cost us great labour, as it has been a
problem since the time of Linnaeus. But we have killed or badly injured a multitude of
plants: N.B.--Oxalis carnosa was most valuable, but last night was killed."
His letters of this period do not give any connected account of the progress of the work.
The two following are given as being characteristic of the author:]
CHARLES DARWIN TO W. THISELTON DYER.
Down, June 2, 1878.
My dear Dyer,
I remember saying that I should die a disgraced man if I did not observe a seedling
Cactus and Cycas, and you have saved me from this horrible fate, as they move
splendidly and normally. But I have two questions to ask: the Cycas observed was a huge
seed in a broad and very shallow pot with cocoa-nut fibre as I suppose. It was named only
Cycas. Was it Cycas pectinata? I suppose that I cannot be wrong in believing that what