448 MR. POTTER ON DEVELOPMENT OF STARCH-GRAINS IN 
The formation of starch on parts of plants not green has been 
investigated by Schimper*. He finds that the starch-grains on 
these parts are formed by deposition through the agency of 
starch-forming corpuscles. In polyhedral cells, where the nucleus 
is suspended from the parietal layer of protoplasm by strands of 
protoplasm, the starch-forming corpuscles are generally differen- 
tiated out of the layer of protoplasm which surrounds the nucleus, 
and consist of modified protoplasm. 
The starch is formed either in the interior of the starch-form- 
ing corpuscle (Colocasia, endosperm of Jelandrum) or in the 
peripheral parts (Philodendron, Amomum, Phajus, Canna). After 
the first formation of the starch, the starch-forming corpuscle for 
some time increases in size, the starch at the same time being en- 
larged. When, however, the starch-forming corpuscle has attained 
its maximum size, it continually decreases and finally disappears, 
the starch-grain constantly being enlarged as long as any part 
of the starch-forming corpuscle remains in contact with it. The 
starch-grains formed in this manner are usually excentric ; the 
broader part being caused by a more active deposition of starch, 
is that part which is in contact with the starch-forming corpuscle; 
and consequently the hilum, which is that part of the grain which 
is first formed, is in that part of the starch-grain which is furthest 
removed from the starch-forming corpuscle. 
a, b, c. Starch-grains enclosed in starch-forming corpuscle, which in a and b 
has contracted except towards the extremities of the rod. At e the starch- 
forming corpuscle is partially swollen, and at d much more swollen. 
In tracing the development of the rod- or bone-shaped grains 
of starch of the Euphorbiacez, I find that they are developed in 
the interior of rod- or spindle-shaped starch-forming corpuscles, 
which lie in the parietal protoplasm of the cell. The starch-grain 
is at first visible, through the agency of iodine, as a thin streak 
in the interior of the starch-forming corpuscle. This streak, 
through the deposition of starch, assumes a rod- or spindle-shape; 
it inereases in length and breadth, the starch-forming corpuscle 
at the same time increasing. When the starch-grain has attained 
* Bot. Zeitung, 1880 and 1881. 
