THE MOVEMENTS OF PLANTS. 
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bends over until it rests on and forms a roof over the edges 
of tbe now vertical lateral leaflets (fig. 15). 
Coronilla rosea . — This plant affords an instance of leaflets 
rising at night from having been horizontal during the day. 
The leaflets at the same time bend backwards towards the base 
of the petiole, until their mid-ribs form with it angles of from 
40° to 50° in a vertical plane (PI. Y. fig. 16). 
Cassia corymbosa, during the day ; and the same, asleep, at night. 
Cassia . — The nyctitropic movements of the leaves in many 
species of Cassia are highly complex. Mr. Darwin’s observa- 
tions were made chiefly on C. floribunda and corymbosa, and he 
furnishes the following description. The horizontally extended 
leaflets sink down vertically at night, but not simply, as in so 
many other genera, for each leaflet rotates on its own axis, so 
