1921] SCHERTZ—MOTTLING 121 
phyll, and has proved that plants with much chlorophyll show 
little or no breaking up of chlorophyll by light, and that plants 
with little chlorophyll (as Elodea) show as much as 31 per cent of 
the chlorophyll broken up by light in seven hours. IwANowsKI 
also showed that colloidal solutions were about sixteen times as 
light stable as molecular solutions, and the more concentrated the 
colloidal solution the more light stable it becomes. HERLITZKA 
(20) also found that the chlorophyll exists in the leaf in the colloidal 
state. 
In view of these facts one might expect light lability to enter 
as a factor in the decomposition of chlorophyll in Coleus, for the 
chlorophyll is only one-fifth as concentrated as it is in most other 
sun plants. 
Borescu (6) in his experiments on algae (Phormidium corium) 
showed that the algae when grown on nutrient media changed 
from a dark green, after two months, to gold or red brown. Addi- 
tion of more of the nutrient media caused them to resume again 
their green color. He believes that the change of color back to 
the natural green was due to the presence of the nitrogen in the 
potassium nitrate. Any nitrate, ammonium salt, or other nitrogen 
compound would do the same. Other plants, such as Chlamy- 
domonas, Hydrodictyon, and Oedogonium, depend upon nitrogen 
compounds for their existence, and also the building and accumu- 
lation of chlorophyll depends upon the available nitrogen supply. 
Extractions of the pigments were made by Borescu, who found 
that the green Cyanophyceae showed the normal colors (chlorophyll, 
phycocyan, and carotin), while the brownish extracts of these 
algae showed little chlorophyll and much of the carotin. He 
believes that the brown color was due to the breaking down of 
the chlorophyll and phycocyan, which are closely related in their 
origin. He also noted that the carotin increased as the chlorophyll 
and phycocyan broke down. In the case of higher plants, BoREscH 
noticed that nitrogen had a greening effect upon the plants. When 
nitrogen was failing and the leaves were getting yellow, additions 
of manure kept them green. ARTARI (2) found that chlorophyll 
formation and the quantity of chlorophyll depend upon the sub- 
stratum. Stichococcus bacillaris, when grown in the dark with 
