460 MR. A. J. EWART ON ASSIMILATORY INHIBITION. 
Conclusions. 
By the operation of a variety of agencies a condition of 
assimilatory arrest or inhibition may be induced in living chloro- 
phyllaceous cells and tissues. These are: dry heat, moist heat, 
cold, desiccation, partial asphyxiation, etherization, treatment 
with acids, alkalies, and antipyrin, accumulation of the carbo- 
hydrate products of assimilation, immersal in very strong 
plasmolytie solutions, and prolonged insclation. 
The inability to assimilate is, if the cell remain living, only 
temporary, being followed sooner or later by a more or less 
complete recovery of the power of assimilation. 
During the whole time in whieh the power of assimilation 
is absent, the cell continues to respire. By the direct effect of 
each particular agency, the respiratory activity may in some cases 
be but little affected (etherization, over-accumulation of carbo- 
hydrates), in one ease is increased (moist heat), but in most is 
diminished (cold, desiecation, immersal in strong plasmolytic 
solutions). The question, whether or not an after-effect may also 
be produced on respiration, is unable sensibly to affect the results 
obtained as regards assimilation. If the inhibition of assimila- 
tion experimentally produced be permanent the cell finally dies 
aud ceases to respire. 
In the great majority of cases no visible change in the chloro- 
. phyll or the chlorophyll grain is associated with the stoppage of 
assimilation. In such cases the assimilatory arrest probably 
originates in the plasmatic stroma of the chlorophyll corpuscle, and 
may be due to some breakage in the necessary vital connection 
between the assimilatory pigment and the assimilatory plasma. 
Most of the above inhibitory agencies operate by checking or 
arresting the initial stages or primary processes of assimilation 
(decomposition of CO, and formation of carbohydrate); but since 
the accumulation of carbohydrate affects assimilation, any cause 
interfering with the rapidity of its removal from the assimilatory 
cells may also finally affeet their power of assimilation. 
Henee in the plant, as a whole, assimilation may be influenced 
by causes operating upon the general cell protoplasm and 
affecting the later stages in the process of assimilation (absorp- 
tion, elaboration, and transformation of the assimilated carbo- 
hydrates), either of the assimilatory cell itself or of the cells 
which are dependent upon it for their supply of carbohydrate 
