414 MR. A. J. EWART ON ASSIMILATORY INHIBITION. 
of tannin and other substances which the penetrating ammo- 
nium carbonate causes to be excreted. The phenomenon is 
therefore a proof that the alkali penetrates both the cell-wall 
and the lining protoplasm. 
For experiments upon assimilation a 0-1-per-cent. solution of 
ammonium carbonate (0:1 gramme of salt to 100 grammes H,O). 
was employed. In this strength of solution the movement of 
B. Termo remains active as long as oxygen is present, and hence 
the specimens can be examined after immersion in a 0'1-per-cent.. 
without being washed or can be examined directly in it. To see 
whether recovery is possible or not it is of course necessary to 
remove all alkali by washing in either fresh water or water con- 
taining a trace (0:001 per cent. H,PO,) of acid. 
Chara fragilis is killed by 16 hours’ immersion in a O'1-per- 
cent. solution, but after 10 hours’ immersion, though most end 
and cortical cells are dead, a few are living and normal in 
appearance, but show neither rotation nor assimilation. After 
washing, in a few cells after 1 hour, a faint evolution of oxygen 
may commence, and in some cases this is shown at the end or 
middle of a cell only, over the rest of the cell no evolution of 
oxygen being shown, but after an hour or so spreading over the 
whole of the cell. In 2 hours a weak evolution of oxygen is 
shown from all the living cells, but still no rotation. In 3 hours 
slow rotation is shown, and after 6 hours all the cells which now 
remain living show moderately active rotation and assimilation. 
The results obtained with Elodea and Utricularia are given 
in Table X. It will be noticed that apparently a two days' 
immersion produces a less marked effect upon assimilation than 
that produced during the first 16 hours. The reason is that the 
plants gradually withdraw more and more of the alkali from the 
solution, which at the same time loses ammonia by evaporation, 
so that although more than a litre was used in each case, at the 
end of two days only the very faintest trace of alkalinity was 
present. In this weakened solution a partial recovery may, if 
the action has not proceeded too far, take place. 
Iu another experiment the plants were kept for two days in 
a O'l-per-eent. solution several times renewed. Elodea was 
entirely killed; in Utricularia a few branches remained living 
and showed no assimilation, after 5 hours in water in a few cases 
weak but mostly still none, and after 1 day all living branches 
showed distinct assimilation, in most cases fairly active. 
