Darwin is getting old but he continues working unrelentingly. One year
before his death the book on movements of plants comes out. He had written
earlier on this subject in the book on climbing plants. This new book was
called: Power of movement in plants.
The book discusses all possible movements made by plants: sleeping movements,
tendril movements, pushing aside earth by germinating seed, spreading the
leaves in order to catch more sunlight, movements of the stem (sunflower),
the fact that some seeds screw themselves into the soil, etc.
He asked his friends and acquaintances to send him certain plants to do
experiments on these in his greenhouse. In the book 320 (!) species are
discussed.
On the photo a Hypericum (St. John's-wort) which closes its flowers
at the first rain drops. |
Darwin recorded the movements of plants in the following way. He glued
a glass fiber with a drop of shellac on a spot on the plant he intended to
observe. Behind the plant a piece of cardboard was placed on which a dot
of Indian ink was put. In front of the plant a glass plate was placed. At
regular time observations were made. The observer placed himself in that
way that he could see the litte shellac ball and the black spot in one line
and then put a dot on the glass plate. Later on the dots were connected by
lines. The complete figure was copied on paper. See the page from the book
above.
The book is rather boring to read, but yet it formed the basis for a new
branch of science. |
