certain Tropical Trees. 83 
earlier, as many as fifteen pairs of leaflets were pendent, and 
at 6.30 twenty-eight pairs. 
Here, then, it may confidently be asserted that, as in 
Brownea grandiceps, the position of the leaflets with respect 
to the vertical is daily determined by the amount of sunshine ; 
and that here also, as already demonstrated, in Brownea 
grandiceps , the amount of daily depression ultimately deter- 
mines the plane taken up by the mature leaflet when, after 
weeks during which the extent of movement has been gradu- 
ally waning, this leaflet assumes a fixed position. 
The movement described, whereby the leaflets sink down- 
ward so as to expose their edges to the light, resembles in 
purpose that of Robinia Pseud-acacia ; in this plant, however, 
the leaflets remain motile by virtue of their pulvini, whereas 
in Amherstia nobilis and species of Brownea the leaflets 
become ultimately fixed in a position of which the chief 
determinant is the amount of insolation received. 
The movement of the leaflets of Robinia is such that during 
darkness they point downward, in dull light they stand out 
approximately horizontally; in intense sunlight they rise up 
and present their edges to the light 1 . 
Wiesner showed by direct experiment that this adaptation 
of the power of leaf-movement, so common throughout the 
Leguminosae, has, in the case of Robinia Pseud-acacia , for its 
purpose the protection of the chlorophyll from too intense 
sunlight 2 . 
The movements effected by the leaflets of Averrhoa bilimbi 
in response to bright sunlight have probably a similar signifi- 
cance; and these movements are of exactly the same nature 
as those which occur in the trees of the genera Anther stia, 
Brownea and Humboldtia. But A verrhoa bilimbi has a periodic 
movement which results in a hanging of the leaflets toward 
evening, and a horizontal outspreading of the leaves in the 
morning ; whereas, as has been described, the leaflets of 
Brownea grandiceps, &c., when growing in the diffuse light of 
1 Darwin, Power of Movement, pp. 355 and 445; and Wiesner, loc. cit., p. 27. 
2 Wiesner, loc. cit. p, 26 et seq. 
G 2 
