Page:The Journal of Indian Botany, Volume III.djvu/166

 THE

Journal of Indian Botany.

Vol. III. MARCH, 3923. No. 5.

The sleep movements of plants were known to the ancients, having been first noted, according to Pfeifer (10), by Pliny. According to the same author Linnseus was the first to draw attention to the common occurrence of such movements.

Later authors from De Candolle (4) to Hofmeister (8) appear to have held the view that such movements were due to a hereditary periodicity. Pfeffer (10) first showed in 1875 that these theories were untenable and he considered that the movements were due to either photonastic or thermonastie responses or a combination of the two. He proved that while a daily periodicity does exist, yet it only persists for a few days at most under constant conditions, and is in no way hereditary.

Darwin (3) added many facts and figures a few years later, but his view that all daily movements are the result of circumnutation does not appear to be tenable, and has not been generally accepted.

The known facts were well summarised by Kerner (9) in 1895, since when no one else has, so far as the author is aware, given a fuller general account of these movements than was given by him.

Physiologists, some of whom have been mentioned above, have repeatedly endeavoured to explain the causes which determine the nature of such movements, but with little success.

The present paper suggests a fresh view point from which the object may be regarded, and which the writer hopes may put the