428 MR. A. J. EWART ON ASSIMILATORY INHIBITION. 
the cells can recover and become green again. Similarly the 
secondary chlorophyll grains which Dehnecke (J. c.) describes 
as appearing in many cases after the primary chlorophyll grains, 
loaded with starch, have lost their starch, disintegrated and 
disappeared, are either formed from the latter or are simply the 
same grains in a different condition. On the other hand, the 
fact that in young cells and organs chlorophyll corpuscles may 
be formed and differentiated where none were previously present 
(Schimper) *, is proof positive that the chlorophyll corpuscle is 
simply a specially modified and differentiated portion of the 
protoplasm of the cell, resembling the nucleus somewhat in the 
structure and nature of its plasma and in being bounded 
(according to some authors) by a distinct limiting membrane, 
but differing in its infiltration with chlorophyll and in being 
specially differentiated to form the centre or focus for the process 
of assimilation. 
Though the chlorophyll body is specialized simply and solely 
for assimilation, it does not follow that this function will not be 
affected by changes in, or by causes influencing, the general 
protoplasm of the cell. It is only the first stages of plant assimi- 
lation which are restricted to the chlorophyll body, those which 
consist in the conversion of simple inorganic compounds (water 
and CO,) into more complex and organic compounds (sugar and 
starch); the final processes of assimilation, in which dead organic 
or inorganic compounds are built up into living protoplasm, are 
carried on by the general protoplasm of every cell, whether 
animal or plant. Any cause which acts upon the general cell 
protoplasm and stops or hinders either the later stages of assimi- 
lation or the removal of the accumulated assimilatory products, 
will also react upon the first stages of assimilation, 7. e. assimi- 
lation by the chlorophyll body, hindering or stopping this also. 
Thus Saposchnikoff * has shown by experiments with cut leaves 
of Vitis and Rubus, that when the carbohydrates present reach a 
certain percentage no more are produced. In Vitis Labrusca 
* A. F. W. Schimper, “ Untersuchungen über die Chlorophyllkérper,” 
in Pringsh. Jahrb. Bd. xvi. 1885. 
T W. Saposchnikoff, “ Ueber die Grenzen der Anháufung der Kohlenhydrate 
in den Bláttern der Weinrebe und anderen Pflanzen," in Ber. d. D. Bot. Ges, 
Bd. ae 1891, p. 293. Also preceding papers in 1890 and 1889, p. 258 and 
p. . 
