Carbon Assimilation. 
247 
phyll. Herlitzka (1912) has shown that the spectrum of living leaves 
agrees with that of colloidal chlorophyll solutions while both differ 
in the same way from the spectrum of true chlorophyll solutions. 
Willstatter’s own experiments confirm the observations of 
Herlitzka. He made measurements of the hands in the spectrum 
of leaves of different plants and found them to occupy the same 
positionsas the absorption bands of the spectrum of colloidal solutions 
of pure chlorophyll a. 
Again the condition of the chlorophyll in fresh leaves is altered 
if the leaves are plunged in boiling water. After such treatment 
the chlorophyll is much more easily extracted. Microscopic 
examination shows that the chloroplasts are deformed as a result of 
such treatment, they are displaced from the normal position in the 
cell and diffusion out from them of chlorophyll follows almost 
immediately. Externally the leaves change in colour to a deep 
green. Spectroscopically this change in colour is shown to be 
accompanied by a displacement of the absorption bands towards 
the violet end of the spectrum so that they occupy practically the 
same position as those in the spectrum of a chlorophyll extract. 
This is explained at once on the view that the chlorophyll has 
changed from a colloidal to a true solution and is now dissolved in 
waxy substances which have become liquid as a result of the 
alteration of temperature. As would be expected, pure acetone and 
ether easily extract the pigment from a powder made from leaves 
previously steeped in boiling water. 
It is worth mentioning that if fresh nettle leaves are treated 
with acetone or other solvents, and are then examined spectroscopi¬ 
cally when they have become deep green but before any pigment 
has diffused out of the tissues, the same bands in the spectrum are 
observed as with the spectrum of the extract. It is thus possible to 
obtain within the leaf tissue a solution of the same kind as that 
obtained by extraction. 
The various chlorophyll samples obtained by Wiilstatter by 
different methods of extraction are identical, whether obtained from 
fresh leaves, or from leaves put in boiling water, or from dried leaves. 
They showed no difference in chemical composition, solubility or 
optical properties. 
While in the higher land plants examined the same four pigments 
are always present, and the ratio of the quantities in which the four 
are present does not vary very much, Wiilstatter found a somewhat 
marked variation in the green algas, and a very different state of 
affairs in the brown algae. 
The green alga examined was Ulva lactuca. Here were found 
