DR. A. J. EWART ON ASSIMILATORY INHIBITION. 555 
alone by the chlorophyll grains will cause them to attract the 
Bacteria employed, and by inducing streaming currents in the 
surrounding fluid cause the Bacteria floating in it to move also. 
He concludes that Engelmann’s observations of the evolution of 
oxygen (1) by etiolated cells, (2) by isolated chlorophyll grains, 
(3) the secondary maximum in the blue, are due to this error. 
The objection is, however, quite unfounded. The physical 
movement of particles suspended in a fluid or streaming in one 
direction cannot possibly by even the most careless observer be 
confounded with the active and almost purposeful translatory 
movement of B. Termo in the presence of oxygen. The supposed 
error due to the absorption of heat-rays by the pigmented 
chlorophyll grains or coloured cell-contents, causing them to 
attract the Bacteria in the surrounding fluid, has conclusively 
been proved by Engelmann * to be non-existent. 
The fact that isolated chlorophyll grains can assimilate and 
the presence of an assimilatory maximum in the blue can now, 
however, be regarded as well established. 
The question as to whether the observations upon the presence 
of the power of assimilation in etiolated plants were correct or 
not seemed, however, worthy of further prooff. It is well 
known that in certain plants, even though developed in complete 
darkness, the leaves and chlorophyll grains become green. Such 
chlorophyll developed in darkness might not, however, be identical 
with that developed in light, and the chlorophyllaceous cells 
might possibly be at first, as regards the function of assimilation, 
in an etiolated condition, possessing at first only a weak power 
of assimilation or none at all The following results obtained 
with Pinus pinea answer the above questions :— 
* Engelmann, Bot. Zeitg. 1887, p. 107. 
t The Bacterium method was employed as a test for the power of evolving 
oxygen in light. To the details given by Engelmann in the preceding paper 
it is only necessary to add that when B. Termo is cultivated upon Agar, for 
generation after generation, its vegetative vigour finally weakens, the motile 
condition lasts for a shorter and shorter time, and long non-motile Bacillus 
threads may be produced. On examination such cultures are found to be pure 
and really monotypic, but in the fresh cultures from isolation the threads soon 
reappear, In practice it is advisable to re-isolate the Bacterium (from the 
integuments of Peas, &c.) every month or so. 
