F. F. Blackman. 
38 
subsequent minutes in the dark. The method is said to be sensitive 
enough to show the oxygen produced by illuminating with a single 
match. 
The photo-synthetic power of this leaf-extract lasts for some 
hours and then begins to fail, which led Beyerinck to hold that the 
co-operation of the residual activity of protoplasm (dissolved!) is 
involved in the photo-synthesis. The most recent paper on the 
subject is by Molisch who confirms Beyerinck’s results, but points 
out that his filtered leaf-extract contains complete chloroplasts and 
solid pieces of cytoplasm, etc. to which the photo-synthesis maybe 
due. Ewart had already shown that isolated chloroplasts photo- 
synthesise and so attract the oxygen-loving bacteria of the 
Englemann method. Molisch finds that the leaf-extract loses its 
power immediately on boiling, but that it can be evaporated at 
ordinary temperatures and kept dry for a few days with only a 
partial diminution of its activity. 
From leaves dried at a temperature of 35°C an active extract 
too is obtained but not so from leaves dried at 100°C. All extracts 
lose their power when passed through a fine porcelain filter which 
removes all solid particles whatever. 
Laminin album was found to give the most potent extract, 
while with many plants some secondary cause destroys the 
activity in the process of extraction. In trying to sum up the 
researches on this particular point we are brought up by a mass of 
divergent statements so contradictory as to be, on any hypothesis, 
rather discreditable to our subject. 
The work of Molisch carries with it the greatest conviction 
and leads one to conclude that photo-synthesis can exist to a small 
degree apart from the living cell. One may further hazard the 
hypothesis that this function is correlated with some machinery 
more complex than an enzyme but much less complex than a 
complete protoplasmic unit. 
A hopeful direction for seeking further light on the problem 
should be by way of determining whether an active extract can be 
obtained from cells which have been robbed of their power of 
assimilation by such special treatment as the leaf mentioned in the 
previous footnote. 
BIBLIOGRAPHY. 
Buchner. Ber. d. deut. chem. Gesell. Bd. 30, 31 and 32, 1897-99 etc. 
Macfadyen, Morris & Rowland. Proc. Roy. Soc. Vol. 67, 1900. 
