DR. A. J. EWART ON ASSIMILATORY INHIBITION, 575 
though such undoubtedly originally existed, and may have, as 
has been previously shown, remained living for more than a 
week. Several cells were, however, seen in which scattered 
green chlorophyll grains were present at one end only, at the 
other only dead colourless chlorophyll grains being present, this 
part showing absolutely no evolution of oxygen, the other weak 
or very faint. 
The dead chlorophyll grains remain in the ectoplasm and do 
not leave the wall, as was the case in the experiments mentioned 
by Pringsheim, in which by means of sunlight he killed the 
chlorophyll grains over small exposed areas of cells of Chara and 
Nitella. It is commonly only where a large number are living 
that green chloroplastids are found interpolated between the dead 
colourless ones. The reason why no internal regeneration and 
proliferation of the chlorophyll bodies takes place is because the 
cells were, when exposed, fairly adult. In the younger parts, 
which remain living and capable of growth, renovation does take 
place and normal green parts are finally produced. 
Where less than Z or so of the original amount of chlorophyll 
is present, supposing that in Chara there is a somewhat similar 
relation between respiration and assimilation as there is in 
Phanerogams, where an assimilatory tissue such as a leaf can 
assimilate, under the most favourable conditions, from 20 to 30 
times the amount of CO, that it can respire in the same time, 
then this amount of chlorophyll will, especially bearing in mind 
the fact that under normal conditions during half the time the 
plants are in darkness, be unable to assimilate sufficient carbon 
to compensate for the amount lost by respiration, and partial 
starvation must ensue until the quantity of plasma is reduced to 
an amount corresponding with the lessened amount of chlorophyll 
present. This is actually the case, for in such cells the endo- 
plasma is much thinned and consequently the rotation in it 
also difficult to observe; whilst the ectoplasm, containing as it 
does from 4 to 4 its bulk of dead chlorophyll grains, is also 
lessened in amount. That the ectoplasm surrounding the dead 
chloroplastids remains living is shown by the fact that signs 
indicating a distinct growth and elongation of the cell-wall 
subsequent to the killing of the original chlorophyll layer can 
frequently be noticed. The chlorophyll grains found present in 
such cells are ones which have escaped the fate which befell their 
brethren owing to their accidentally being protected by being 
