Denniston—The Structure of the Starch Grain. 533 
possible that the substance first formed from starch by the a.Cr 
tion of diastase is the same that is present in the orange layer 
in the formation of the grain. As an hypothesis it may he 
suggested that a. viscid mother substance, as Mikosch believed, 
which becomes more and more concentrated by additions' from 
without, until layers of starch are laid down on its inner sur¬ 
face. In the young grains starch is deposited equally all round, 
but soon the grain by its growth stretches the plastid, and the 
granular substance inside is too viscid to allow the addi¬ 
tions from the thicker part, to spread readily to the mother 
substance at the opposite end of the grain, under the thinner 
part of the plastid. In this manner the mother substance un¬ 
der the thicker part of the plastid, soon becomes saturated and 
it is on this side) that the thick portions of the starch, layers' are 
deposited. This assumption is in harmony with the fact that 
when the eccentric layers begin to' form they are simply thin¬ 
ner on the anterior end, then they become incomplete and fin¬ 
ally are laid down on the posterior end only. 
REFERENCES. 
1. Hageli, 0.: Zeit. fur Wiss. Bob, 1847, p. 119. 
2. von Mohl: Bob Zeit., 1859, p. 225. 
3. Gffiger: Bob Zeit., 1854, p. 41. 
4. Mikosch: Sitzungsbericht d. Wiener Akad., 1885. 
5. Meyer, A.: Untersuchungen fiber die Starkekorner, 
1895. 
6. Salter: Jahr. Wiss. Bob, 1898, p. 117. 
7. Timberlake: Bob Gazette, 1900, p. 97. 
