MR. A. J. EWART ON ASSIMILATORY INHIBITION. 411 
It is not therefore concomitant with any loss of assimilatory 
power. (In many cases the leaf-cells of Dicranum, especially 
at the bases of the leaves, exhibit a marked longitudinal striation, 
somewhat resembling that shown by a voluntary-muscle fibre. 
As before, the presence of this striation is quite independent of 
the presence or absence of assimilation, and disappears in a day 
or two if the cells remain living. In all cases the chlorophyll 
grains remain normal and unaltered whether assimilation be 
present or absent so long as the cell remains living. 
Effects of Treatment with Acid upon Assimilation. 
The acid employed was phosphoric acid, a 1-per-cent. solution 
being made by adding to 1 c.c. of a thick sirupy solution of 
H,PO,, 99 c.c. of water. A very dilute acid solution suffices 
to inhibit the movement of B. Termo. Thus in a 0'001 per cent. 
solution the movement continues apparently unaffected, in a 
0:005 per cent. solution it remains but is not so active, in a 0:01 
per cent. solution it slows and stops in a few minutes. 
If preparations of end cells of Chara be made in a few drops 
of 0:01 per cent. H,PO, in closed cells with Bacteria, rotation is 
soon slowed and in half an hour has in most cells ceased, though 
in others it is fairly active. As rotation ceases it undergoes 
temporary increases, attaining almost normal rapidity for a few 
minutes or so and then slowing again. These increases become 
shorter and less frequent, and finally the rotation comes to a 
standstill. In half an hour the Bacteria, which were at first 
motionless, begin to move, at first slowly whenever oxygen is 
present, and later more rapidly as the acid is absorbed by the 
Chara filaments. The cells in which rotatiou is still present 
show a weak but distinct evolution of oxygen. In about 2 hours 
rotation has stopped in all cases, but the evolution of oxygen 
does not cease for another 30 to 60 minutes ; and now the power 
of recovery is completely lost, i. e., with short exposure to, for 
Chara, relatively strongly acid solutions rotation ceases before 
the evolution of oxygen does, and when the power of assimilation 
ceases to be manifested, recovery is no longer possible. 
Plants of Chara are fatally affected by immersion for several 
hours in a 0'001 per cent. solution of H,PO,, provided that a 
sufficiently large quantity of the acid solution is employed and 
that the specimens are quite free from chalk. Chara is exces- 
sively sensitive to immersion in acid media, and far more so 
LINN. JOURN.—BOTANY, VOL. XXXI. 26 
