1921] SCHERTZ—MOTTLING II9 
pigments absorb blue and especially violet rays, whose power to 
break down chlorophyll is especially high. It is of interest to 
notice how the carotin content varies under different conditions. 
The amount of carotin in a leaf varies according to the seasons 
of the year (40), being greatest during the flowering period in 
nettles and horse chestnuts. In vetch (40) about five times as 
much carotin exists in the green leaves as in the etiolated ones. 
Ewart (16) has shown that when mustard seedlings were 
grown in the absence of carbon dioxide, more carotin was produced 
than when carbon dioxide was present. He remarks that his 
method of analysis was not wholly accurate, however, and that | 
during the separation of the pigments the losses were so great that 
the exact estimation of the amounts originally present was impos- 
sible. The seedlings grown in air deprived of carbon dioxide were 
TABLE XXIX 
AMOUNTS OF PIGMENTS PRODUCED IN MUSTARD SEEDLINGS 
R 100 GM. OF FRESH MATERIAL) 
COs Chlorophyll | Carotin Xanthophyll 
POON So it wh een ye 0.474 o.11 0.15 
POM cer sets eee 0.271 0.275 9.12 
smaller, darker, and more bluish green. This blue green seemed 
to be due not to an excess of chlorophyll, but rather to the more 
compact character of the tissues, and it appears that chlorophyll 
develops most rapidly when its normal functional activity can be 
exercised. Ewart believes that he is justified in concluding that 
the carotin supplied at least a part of the carbon and hydrogen 
for the construction of chlorophyll. 
Kout (30) showed that etiolated seedlings contained carotin 
in abundance, and even doubted whether any other pigment was 
present. He found that the percentage of carotin did not decrease 
when the etiolated seedlings were exposed to light and chlorophyll 
was formed. He thus denied that carotin was converted into chlo- 
rophyll as was believed by Ewart. Ewart states that while food 
materials were abundant the production of carotin continued at a 
greater rate than it was used in the formation of iin 
