46 



Carbon A ssimilation. 



Table 1. 

 Grams of Pigment in 1 kilo, dried leaves at different times of day. 



Species. 



Yellow Pigments. 



Sambucus nigra 

 Aesculus hippocastanum 

 Platanus acerifolia ... 



5 p.m. 



1-57 

 1-91 

 1-35 



Table II. 

 Ratio of Pigments in leaves at different times of day. 



2. Variations in the Proportions of the Two Chlorophyll Components. 



Willstiitter 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 orop y a j^ 2.35^ ^he greatest difference 

 chlorophyll b 

 from the mean •? to -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 ^, ,"'^°^, ^,, f is 2'93 with extreme variations from 

 chlorophyll b 



this mean of -5 to -6. 



Shade leaves give an average ratio of ^chlorophyll a ^^ g.gl +' 



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. 



