certain Tropical Trees . 
67 
The numbers given below were obtained as in the preceding 
experiment, and represent the average rate in seconds of 
the passage of ten bubbles between the two marks. 
In this case each branch bore ten leaflets and the total 
areas of the three sets of leaves differed but little from one 
another. 
Average rate of passage of ten bubbles : 
Green. Brown-green. Red. 
123 secs. 165 secs. 204 secs. 
Here also, therefore, the green leaves transpire more rapidly 
than the younger red-brown, and both more quickly than 
the youngest red leaves. 
In yet a third case two branches, one of green leaves, the 
other of red-brown, were used. The following are the results : 
Young green leaves (secondary petioles still flexible) ten leaflets, 
Amherstia nobilis. 
6 5 4 
6 5 4 
7 5 4 
5 5 5 
5 5 5 
5 4 4 
5 4 4 
5 4 4 
5 5 3 
5 5 3 
5 
5 
5 
5 
5 
5 
5 
5 
7 
Time in seconds of passage of ) 
air bubble between marks $ ®4 ^7 4 5 2 
Average time in seconds for passage of 10 bubbles = 48. 
Red-brown leaves, twelve leaflets. (Since this experiment 
was used also for another purpose to be mentioned directly, 
no less than 140 readings were taken.) The times in seconds 
per ten bubbles'’ passage are in order: 171, 145, 135, 138, 138, 
I2 4, 137, i5°> I 23> I2 9> I 3 1 > 1 3 6 > 12 9 > 1 3 The average of 
these fourteen numbers is the average time of passage of 
10 bubbles = 130. 
Now the weight of thin paper cut into the shapes of the 
ten green leaflets was 2-3 g. ; that of similar paper cut in the 
