Carbon Assimilation. 
93 
Table I. 
Grams of Pigment in 1 kilo, dried leaves at different times of day. 
Species. 
Chlorophyll. 
Yellow Pigments. 
Sambucus nigra 
4 a.m. 
8-49 
5 p.m. 
8-80 
4 a.m. 
1-48 
5 p.m. 
1-57 
Aesculus hippocastanum ... 
9-58 
8.75 
2-07 
1-91 
Platanus acerifolia... 
6-82 
6-21 
1-06 
1-35 
Table II. 
Ratio of Pigments in leaves at different times of day. 
Species. 
Chlorophyll a 
Carotin 
Chlorophyll b 
Xanthophyll 
4 a.m. 
5. p.m. 
4 a.m. 
5 p.m. 
Sambucus nigra 
2-77 
2-85 
0-621 
0-512 
Aesculus hippocastanum ... 
2-89 
2-82 
0-699 
0-699 
Platanus acerifolia ... 
3-52 
3-34 
0-478 
0-500 
2. Variations in the Proportions of the Two Chlorophyll Components. 
Willstatter found that the composition of chlorophyll present 
in different plants, and in sun and shade leaves of the same plant is 
approximately, though not exactly, constant. 
The mean ratio of ( j 1 * 01 °phyh a j s 2-85, the greatest difference 
chlorophyll b 
from the mean *7 to f 8. 
The variations appear to be produced by the conditions under 
which the leaves are growing. Thus it seems that some plants are 
ill suited for growth in the shade. Leaves of Sambucus for example, 
living in the shade, show abnormal chlorophyll relations, whereas 
real shade plants such as the Beech exhibit a normal chlorophyll 
content. 
On the whole, shade leaves contain relatively less chlorophyll a 
than do normal leaves. For if shade leaves are excluded the 
average ratio of c h lor °phyjj a j s 2-93 with extreme variations from 
chlorophyll b 
this mean of '5 to ‘6. 
Shade leaves give an average ratio of c hj QI0 Phyjj a 0 f 2*61 + 
chlorophyll b 
•55, a number appreciably smaller than the mean for normal leaves. 
The time of day is found to have no influence on the ratio of 
pigments. 
