ON LEAVES. 93 
the movement of the plant known as the Desmodium gyrans, Fig. 
121. This plant belongs to the family of Leguminacee. It was 
discovered in Bengal, in the neighbourhood of Daca, by an English 
lady, named Morison, whose devotion to natural history had led 
her to undertake the Indiah voyage, and who died on one of her 
botanical excursions. 
The leaves of the Desmodium are composed of three folioles. 
The terminal foliole is very large, and the laterals very small, but 
these last are almost always 
in motion. They execute 
little jerks somewhat anal- 
agous to the movements of 
the seconds of a watch. 
One of the folioles rises 
and the other descends at 
the same time, and with a 
corresponding force. When 
the first begins to descend, 
the other begins to rise. 
The large foliole moves // 
also, inclining itself now We. 1G Dapaodlien gynnen: 
to the right, now to the 
left, but by a continuous and very slow movement when compar 
with that of the lateral folioles. This singular mechanism endures 
throughout the life of the plant. It exercises itself day and night, 
through drought and humidity. The warmer and more humid is 
the day, the more lively are its movements. In India the plant 
has been known to make sixty jerks in the minute. 
This curious plant, which was introduced into Europe for the 
first time in 1777, is cultivated in the Museum of Natural History 
of Paris. The auditors of M. Brougmart’s course of lectures have 
frequently had their attention directed to the strange phenomenon 
of which it is the subject. Its movements occur spontaneously and 
without any apparent cause. But there are movements in other 
plants which are produced by external causes. Such are those of 
the Catchfly andthe Sensitive plant. 
The Dionea muscipula, Fig. 122, is originally from South 
America. Its leaves, which are spread out on the soil near the roots, 
