THE GROWTH AND ORGANIZATION OF THE STARCH 
GRAIN. 
K. H. DENXISTOX. 
(With Plates XXXVIII-XL.) 
INTRODUCTION. 
Perhaps no subject was more studied by the earlier investi¬ 
gators of the plant cell than the starch grains and the plastids 
with which they are associated, and sonic of the first data 
which were established as to the organization of the cell were 
worked out in this connection. In more recent years the nu¬ 
cleus and its functions have claimed an excessive share of the 
attention of cytologists, and the recent summaries of our knowl¬ 
edge of starch and plastids show little advance beyond the 
discoveries of Schimper and Schmitz. Visible stages in the 
process of starch formation are still unknown, with the excep¬ 
tion of one or two discoveries to be mentioned later. 
The main steps by which our present views of starch and 
plastids were developed may be briefly summarized as follows: 
Our real knowledge of starch formation and the function of 
the chlorophyl bodies dates from the work of Sachs in 1862 
(31, p. 365). In this paper Sachs advanced the doctrine that 
the starch in the chlorophyl grains is the first visible product 
of assimilation, a doctrine which has stood to the present time 
for the chromatophore without pyrenoids. This is the cur¬ 
rent statement of the textbooks. Timberlake, however (39, p. 
624), has found that in Hydrodictyon the starch grains are 
formed from segments of the pyrenoids, so that in this case 
the starch is not the first visible product of assimilation. 
