THE 
NEW PHYTOIiOGIST. 
Vol. XV, Nos. 9 & io. Nov. & Dec., 1916. 
[Published January 9th, 1917]. 
CARBON ASSIMILATION. 
A Review of Recent Work on the Pigments of the 
Green Leaf and the Processes connected with them. 
By Ingvar Jorgensen and Walter Stiles. 
(Continued from p. 193). 
C. The Carbohydrates of the Leaf. 
The presence of starch in the leaf was recognised hy von Mohl 
as long ago as 1837, but it was Sachs (1862, 1864) who identified 
this starch as a product of assimilation by showing that it appeared 
in the chloroplasts after exposure to light and disappeared in the 
dark, and he also showed that chlorophyll was necessary. Sachs’ 
conclusion that starch produced in the chloroplast is the first 
visible product of assimilation is well known. The method of 
detection of starch by decolorisation of leaves by alcohol and 
subsequent treatment with an alcoholic solution of iodine is still the 
current method of detection of starch in the plant. 
It was later recognised that many leaves never elaborate starch 
and A. Meyer (1885) classified plants into classes according to the 
quantity of starch their leaves contain. Leaves forming little or no 
starch were known to yield extracts which reduced cupric solutions 
and which were optically active, and it was therefore concluded that 
such leaves contained reducing sugars. In addition the non-reducing 
disaccharide cane sugar was actually extracted in a crystalline form 
from leaves of Vine by Kayser (1883). 
Brown and Morris (1893) justly pointed out that there was no 
proof that the cupric reducing substances in the leaf were sugars, 
and they therefore tested for different sugars. They state that the 
