i8o Ingvar Jorgensen and Walter Stiles. 
Table XVI. 
Assimilation Numbers of Leaves from the same Plant , 
but in different Stages of Development. 
25° 5% C0 2 48000 lux. 
Species. 
Age of 
the Leaf. 
Weight 
of 
Leaves 
Dry 
Weight 
Leaf 
Surface 
Chloro¬ 
phyll 
C0 2 ass. 
in 1 hr. 
Ass. 
No. 
gm. 
gm. 
cm2. 
mg. 
gm. 
Acer 
4-6 leaf at 
pseudo- 
platanus 
the top of the 
branch 
60 
20 
358 
5 
0 059 
11-8 
23rd June 
leaves from 
the base of 
the branch 
60 
2-15 
469 
24 
0124 
5-2 
same day 
Tilia 
young light 
green leaves 
80 
2-05 
421 
5-2 
0 074 
14 2 
25th June 
lower dark 
green leaves 
8-0 
2-55 
530 
22-5 
0148 
6-6 
26th June 
Taxus 
young 
• 
baccata 
branch 
27th June 
20 
5-65 
27-6 
0 131 
4-7 
last year’s 
branch 
28th June 
20 
7-05 
— 
47-5 
0-102 
2-1 
It will be observed from this table that the chlorophyll content 
increases with the age of the leaves ; so does the assimilatory power, 
but not in the same degree. Consequently the assimilation number 
decreases. 
Further data in regard to the variation of the assimilation 
number with the state of development of the leaves are given in the 
following table. 
Table XVII shows clearly that after a time, although the 
chlorophyll content increases, yet the assimilation number 
diminishes. From this fact Willstatter concludes that the chloro¬ 
phyll is present in excess, while some other internal factor (enzyme) 
is limiting the rate of assimilation. 
Autumn Leaves. 
In autumn leaves the conditions are very complex. The general 
rule is that with decreasing chlorophyll content the assimilation 
decreases as is shown in Table XVIII. Leaves rich or poor in 
chlorophyll give the same assimilation number. 
