certain Tropical Trees . 63 
the older observations of Pringsheim and Wiesner 1 i it is 
known that intense sunlight does, in many cases, cause 
considerable destruction of chlorophyll within the leaf. More 
recently also, J ohow 2 * thus sums up this view: ‘The more 
likely view as to the destruction of chlorophyll by light is 
that it acts indirectly .... and on this it is clear why 
destruction occurs more readily in shade-loving plants than 
in typical sun-plants and in young not fully green organs. 5 
I shall bring evidence to show that these trees, Brownea 
species, &c., are shade-loving trees. Accepting this for the 
moment, it will be seen that the young leaves of such trees, 
since they remain tender so long, are just those which might, 
unless specially protected, be expected to suffer from exposure 
to intense sunlight. 
To test Stahl’s results I took a branch bearing young 
red foliage from a tree of Amherstia nobilis . The branch 
was cut under water and its cut end kept in water during 
the experiment. It was so adjusted that the leaflets of 
one side of one of the large pinnate leaves hung vertically 
downward, those of the other were held each in a hori- 
zontal plane. These horizontally disposed leaflets lay 
on moist blotting paper, and were kept flat by means of 
bulldog clips. After five to six hours, pieces, each 50 sq. cm., 
were cut from an equal number of leaflets of the two sets. 
These were extracted in a mortar with similar quantities 
of alcohol, and when the extraction was complete the green 
colour of the two alcoholic solutions of chlorophyll was 
compared. That from the leaflets horizontally placed was 
distinctly of a lighter green than that from those which hung 
vertically . 
The experiment was repeated with a similar result. So 
that these results point to a conclusion opposite to that 
at which Stahl arrives ; for it must be inferred from the 
1 Wiesner, Die natlirlichen Einrichtungen zum Schutze des Chlorophylls der 
lebenden Pflanze; Wien, 1876. 
2 Johow, Ueber die Beziehungen einiger Eigenschaften der Laubblatter zu den 
Standortsverhaltnissen ; Pringsheim’s Jahrb. der wiss. Bot., Vol. xv, p. 285. 
