Carbon A ssimilation. 
79 
The discovery of Butlerow provides the key, and one may 
indeed wonder that so far it has been so little utilised by plant 
physiologists. The similarity which exists between the blood 
pigment and the chlorophyll of the plant, has often been referred to; 
it is also probable that chlorophyll as well as haemoglobin, binds 
carbon dioxide. Now when sunlight strikes chlorophyll which is 
surrounded by C0 2 , the carbon dioxide appears to undergo the same 
dissociation, oxygen escapes, and carbon monoxide remains bound 
to the chlorophyll. The simplest reduction of carbon monoxide is 
that to the aldehyde of formic acid ; it only requires to take up 
hydrogen, 
CO + H 2 = coh 2 . 
This aldehyde is then transformed under the influence of the 
cell contents as well as by alkalies, into sugar. As a matter of fact 
it would be difficult, according to the other opinion, by a successive 
synthesis, to reach the goal so easily ! Glycerin could be formed by 
the condensation of three molecules, and the subsequent reduction 
of the glyceric aldehyde so formed. 
The formation of sugar in a more complicated way is not 
hereby excluded, and it could very well be possible that plant acids 
under certain circumstances are transformed into this substance, 
which in a thousand different forms helps to build up the body of 
the plant. 
In what manner the cell content acts in order to effect the 
condensation of formaldehyde cannot be concluded beforehand, but 
one can assume that the sugar formed remains bound with it, and 
later, according to circumstances, splits off into carbohydrate, sugar, 
starch or glucoside. This is exhibited at least in the life-history 
of the slime fungi in which at a certain stage, from a mass similar to 
the cell content, a great quantity of cellulose is suddenly different¬ 
iated. In this connection it would be very interesting to examine 
chemically the slime fungi in various periods of their life, and 
determine whether they contain free sugar or free anhydrides, or 
whether from the plasmodium sugar or cellulose could be split off 
in the same way that this takes place in the natural process of 
development.” 
The experimental evidence which has been adduced in support 
of Baeyer’s hypothesis is not of much interest, and in most cases 
an unjustifiable parallel is drawn between experiments carried out 
“ in vitro ” and processes in the cell. So long as our knowledge of 
the heterogeneous system in which these latter take place is so 
