408 Priestly and Irving . — The Structure of the Chloroplast 
The meshes of this sponge-like substance were filled with a green 
colouring matter dissolved in an oily substance. 
Nageli showed that when chloroplasts were placed in a solution of 
cane sugar of a certain strength, or in other suitable solutions, they 
absorbed water, and burst into two valves, which contained the colouring 
matter. 
Timiriazeff 1 repeated Nageli’s experiments and obtained similar 
results, using chloroplasts of Phajus on account of their large size. They 
remained unaltered in sugar solutions of a certain strength, but split as 
the solution was diluted. He tried to get a clearer idea of their Structure 
by microscopic examination with red light, and thought he could see the 
green colouring matter arranged around the outer surface of the chloroplast 
in small granules. These granules appeared as a peripheral ring of black 
specks. 
As a result of the examination of living chloroplasts Wager 2 came 
to the conclusion that they consisted of a mass of green granules imbedded 
in a colourless matrix. In some cases he saw a distinctly fibrillar arrange- 
ment of the chlorophyll, and was able to distinguish between a granular 
structure in the chloroplasts in epistrophe and a fibrillar structure in 
apostrophe. 
His general conclusion was that the chloroplast consisted of a colourless 
ground substance, of a delicate alveolate structure, in which the chlorophyll 
was more or less uniformly distributed. 
This very scanty historical review 3 suffices to bring out certain points 
of agreement and disagreement. 
It is almost universally accepted that the chloroplasts consist of a 
colourless ground substance, presumably proteid in nature, and that the chloro- 
phyll is in some way distributed within this substance. Probably it is held 
in solution in some vegetable fat or oil. 
A point upon which there is disagreement is the distribution of the 
chlorophyll in the granule. 
Some observers state that it occurs in a ring at the periphery of the 
plastid, others that it is diffused uniformly throughout. 
It is evident that this question affects the validity of the observations 
of Nageli and Timiriazeff upon the splitting of the granule. 
As Timiriazeff 4 has previously shown, the distribution of the chloro- 
phyll may be of considerable importance from a physiological point of 
view. The energy transformation taking place in the chloroplast, apparently 
requires that the chlorophyll, absorbing the energy, should be distributed 
1 Timiriazeff, Croonian Lecture, Proceedings of Royal Society, vol. lxxii. 
3 Wager, Presidential Address to Section K, British Association Meeting in South Africa, 1905. 
3 For a fuller historical account see Czapek, Biochemie, vol. i, p. 445. 
4 Timiriazeff, loc. cit., p. 457. 
