62 
Keehle. — -The Hanging Foliage of 
ment with the branch ; then the leaves also, in a way to be 
described, take on a generally more horizontal position. 
Growth within the tropics is often so rapid — so too in 
these trees is the elongation of the parts of the shoot — 
that most observers agree in ascribing to this f waiting stage ’ 
some important biological significance. 
Stahl, who has most recently examined these hanging 
branches, takes this view 1 . He, however, rejects Potter’s 
suggestion and sees in the phenomenon a means of protection 
of the young leaves from the force of rain. He points 
out that, within the tropics, the rainfall is often far heavier 
and more violent than in temperate zones, and that rain 
in the tropics generally falls vertically, owing to the stillness 
of the atmosphere. 
To ascertain whether the young foliage needs the pro- 
tection from the sun’s rays which the pendent position 
affords, Stahl conducted the following experiments : young 
leaves of Mangifera foetida , Humboldtia laurifolia , and 
Brownea hybrida were laid on moist blotting-paper with their 
stalks in water, and exposed for four and a half hours (from 
seven till half-past eleven) to the direct rays of the sun (at 
Buitenzorg). At the end of that time the leaves remained fresh 
and gave no indication of any destruction of chlorophyll 2 . 
Stahl next sought to determine whether the vertically 
downward position afforded the young leaves any protection 
against too great transpiration. He found that, under 
similar conditions of insolation, the fully developed leaves, 
which had arrived at their ultimate position, dried more 
quickly than the young hanging leaves (. Amherstia nobilis 
and Brownea coccinea). He observes that the mature leaves 
obviously require no special protection against too great 
transpiration ; still less, therefore, do the young leaves, if 
they wither less readily, require any protection. 
These conclusions seemed to me surprising, since, from 
1 E. Stahl, Regenfall und Blattgestalt ; Ann. du Jard. Bot. de Buitenzorg, 
Tome XI. p. 146 et seq. 
2 Stahl, loc. cit., p. 148. 
