330 MR. H. H. W. PEARSON ON THE 
movement of the petiole was not observed. In Atylosia rugosa 
the younger leaves assume the sleep-position before the older ones. 
In the sun-position the leaflets stand erect upon the erect petiole, 
the ventral surfaces of the two lateral leaflets being in contact 
with the ventral surface of the terminal leaflet (sce diagram). 
Atylosia rugosa. 
Diagram of a leaf in the sun-position. d — dorsal surface of leaflet ; 
v— ventral surface of leaflet. 
Thus, in passing from the sleep-position to the sun-position, 
each leaflet describes an angle of 180^ upon its pulvinus. In 
Atylosia rugosa the terminal leaflet, in moving into the sun- 
position, becomes erect before the lateral leaflets have become 
vertical, and often before they have left the horizontal position. 
(3) Leaves which move into a profile position during intense 
sunlight, but in which sleep-movements were not observed. 
Crotalaria semperflorens, var. Walkeri.—This plant has long 
horizontal prostrate branches; the leaves are monophyllous aud 
alternate. In strong sunlight the leaves rise up to an erect 
position and stand in two parallel planes, the dorsal surfaces ot 
the leaves of each row being directed outwards. 
Zornia diphylla.—The leaf consists of two small ovate-lanceo- 
late leaflets and a moderately long petiole. In bright sunlight 
the leaflets move upwards and forwards until they are almost in 
the same straight line with the petiole, and include an angle of 
about 30° between their ventral surfaces. 
Desmodium parvifolium.—The leaves are monophyllous and 
