85 
certain Tropical Trees , 
withstand the shock of falling rain, why, it may fairly be asked, 
does the branch and leaf as a whole continue to hang so 
long after its function in so doing is fulfilled ? If the leaves 
are not yet in a condition to withstand the shock of rain, the 
protective value of the hanging branch is rendered void by 
the exposed positions the leaflets now take up. 
It has already been stated that the periodic movement 
continues, though with decreasing amplitude, in the leaflets 
whose petioles seem quite hardened and which are members 
of a leaf whose petiole has reached its mature uplifted position. 
Thus the well-matured leaflets of a leaf which was in its 
final approximately horizontal position showed the following 
alterations in position : 
( + ) 
1) (-) 
Saturday, 
5.30 p.m. 4 
2 
Sunday, 
9.30 a.m. 4 
2 
Monday, 
7 >} 
6 
11 
1.40 p.m. (? 3) 
1 2 
11 
4.30 „ 
3 2 
Tuesday, 
7.30 a.m. 
6 
11 
12.40 p.m. 1 
5 
11 
4-30 „ 1 
5 
Wednesday, 
7.30 a.m. 1 
4-5 
„ 
2.30 p.m. 
5 1 
6.30 „ 
4 2 
This daily movement of the leaflets of Amherstia nobilis 
lasts, then, many weeks. 
In yet a third tree (Htimboldtia laurifolia ), whose young 
branches and leaves hang, the ultimate positions assumed by 
the mature leaves are determined, as in Amherstia nobilis and 
Browne a grandiceps , by the extent to which they are exposed 
to the sun’s rays. 
One of these trees growing in the gardens is almost bush- 
like in habit. The bush is so dense that part is completely 
shaded. Branches of apparently the same age were cut from 
the external exposed and from the internal shaded parts, and 
the positions of the paired leaflets of the pinnate leaves 
estimated. This estimation was effected by placing each 
pair of leaflets in one of three groups, according as (i) the 
