248 
Ingvar Jorgensen and Walter Stiles. 
the same four pigments as are present in higher plants, but the alga 
is comparatively richer in chlorophyll b and also contains, relatively 
to the chlorophyll, more of the yellow pigments than is present in 
the green leaves of land plants. Willstatter gives the following table 
for the pigments of Ulva, the numbers representing parts per 
thousand of fresh thallus:— 
Chlorophyll a... 
0-16 
0-12 
Carotin 
Xanthophyll ... 
.. 0-02 
.. 0-06 
The brown algae stand of course in great contrast to the green 
algae and higher plants as far as their external appearance goes in 
the matter of colour, and many views have been held in regard to 
the presence of pigments causingthis colour. Thus Cohn (1865, 1867) 
supposed the cells of the Phaeophyceae contained a brown pigment 
called phaeophyll nearly allied to chlorophyll. Molisch (1905) 
supported this view. In these brown forms he supposed the only 
pigment present to be a brown chlorophyll derivative which changes 
easily into ordinary chlorophyll when the thallus is immersed in warm 
air or water or is treated with organic solvents. Potassium hydroxide 
reacts with chlorophyll to produce a brown derivative which easily 
gives rise to green compounds, and with this brown derivative he 
compares phaeophyll. 
The theory generally taught in this country, which is the one held 
byTswett (1906,1910) and Czapek (1911), is that chlorophyll is present 
in the plastids of the brown algae but that its presence is masked by 
yellow pigments. The well-known class experiment of putting the 
thallus of a brown alga in boiling water which results in an immediate 
change of brown to green, is usually explained by supposing the 
brown covering pigment to be extracted by the water. Tswett 
s uggests as an alternative explanation the alteration of the yellow 
pigment. 
The completion of the proof that chlorophyll is actually present 
in the brown algae has been made by Willstatter and Page (1914). 
These workers in dealing with the phaeophyll theory of Cohn and 
Molisch show that if the algae contained a pigment similar to that 
produced by the action of potassium hydrate on chlorophyll it would 
give different derivatives when subjected to different treatments, but 
this is not the case. 
A second argument against Molisch’s view is to be found in 
spectroscopic examination of the pigments. The brown chlorophyll 
derivatives give a spectrum quite different from that of chlorophyll, 
there is no absorption in the red, but strong absorption in the green 
