84 Keeble . — The Hanging Foliage of 
a room, and therefore exposed to alternating conditions of 
darkness and of light of medium intensity, tend to assume 
a more or less horizontal position, from which they do not 
deviate nearly so much as when exposed directly to the sun : 
conversely, when growing in very sunny places the leaflets 
tend to be permanently depressed and to show a periodic 
movement of much less range than that which they possess 
when growing in places where the sun has less power. 
If any inference may be drawn from the difference in the 
nature of the movements in Amherstia nobilis , &c., on the one 
hand, and in Averrhoa bilimbi on the other, it would seem 
that, in the former, the movement is more especially adapted 
—if not solely — to protect the leaf from excessive insolation, 
in the latter, power of protection, not only from intense sun, 
but also from night exposure, exists. 
Finally, Johow 1 mentions that a protection against sunlight 
is effected in other of the Leguminosae, e.g. Pithecolobium 
trapezifolium , Acacia macrantha and Cassia spectabilis , by 
means of periodic movements. 
The daily movement commences in the leaflets of Am- 
herstia, whilst the branch and petioles are still in the pendent 
position , and indeed becomes very vigorous during this stage ; 
so much so that the leaflets, which have become green and 
stout, rise up under the combined influences of this movement 
and dia-heliotropism and place their leaves more or less hori- 
zontally — the extent to which they become thus outspread 
being, as already shown, determined by the amount of insola- 
tion they individually receive. 
On Stahl’s, view of the meaning of the hanging habit of 
the shoots, an obvious dilemma presents itself. The branch 
hangs downward for several weeks to enable the leaves to 
avoid rain ; yet, whilst it thus hangs, the leaflets, which have, 
it is true, become tougher, rise up and expose themselves to 
rain. Thus a petiole bearing horizontally disposed leaflets 
continues for one or two weeks to hang vertically. If it be 
that the leaflets are become stout enough now to successfully 
1 Loc. cit. p. 295 
