92 
Ingvar Jorgensen and Walter Stiles. 
dichromate solution and of the yellow pigments as corresponding to 
one another in colour intensity. 
Carotin. 
0 0286 grams per litre. 
Potassium dichromate 
solution, 
2 grams per litre. 
100 mm. 
• • • 
... 
101 mm. 
50 mm. 
• • • 
• • • 
... 41 mm. 
25 mm. 
• • • 
• • • 
... 19 mm. 
Xanthophyll. 
0 0284 grams per litre. 
Potassium dichromate 
solution, 
2 grams per litre. 
100 mm. 
• •• 
• • • 
72 mm. 
50 mm. 
• • • 
• •• 
... 27 mm. 
25 mm. 
• • • 
• • • 
... 14 mm. 
ii. Results. 
7, The Total Content of Green and Yellow Pigments. 
As far as his observations go, Willstatter finds the chlorophyll 
content of leaves varies from 0'6% to 1*2% of the total dry weight, 
the greater number of leaves contain about 0'8% of chlorophyll of 
which three-quarters is chlorophyll a and one quarter chlorophyll 
b. Much bigger variations were observed between leaves from the 
same plant than between the mean contents of leaves from different 
plants. Shade leaves were found to be much richer in chlorophyll 
than sun leaves in proportion to the dry weight, but not in propor¬ 
tion to the leaf surface; for shade leaves, as is well known, are 
often very thin. 
The total content of the yellow pigments (xanthophyll and 
carotin) was found to vary in different leaves from 0T% to 0*2% of 
the dry weight, the xanthophyll contributing from 0 07% to 0T2%, 
the carotin from 0'03 to 0’08%. 
Shade leaves were not found to contain a higher percentage of 
yellow pigments corresponding to their higher content of chlorophyll. 
Leaves collected at different hours of the day were examined; 
the time of day was found to be without influence on the 
chlorophyll content or the ratio of the pigments. As this is of 
importance in regard to the function of the pigments in the 
processes of carbon assimilation we may quote here two tables 
taken from Willstatter’s book to show how slight this variation is. 
