MR. A. J. EWART ON ASSIMILATORY INHIBITION. 425 
Table (continued). 
Vallisneria | In Pfeffer's Nahrlosung (15 times concentrated) weak but 
spiralis, distinct evolution of O from many chlorophyll grains 
in light, ceasing in darkness, but power of assimilation 
is soon lost. In 4 to 5 p. c. cane-sugar evolution of O 
almost imperceptible and soon ceases. In 10 p. c. cane- 
sugar, distinct but weak assimilation in many cases, 
which after 3 hours begins to weaken, and in 4 to 6 
hours has entirely ceased. 
Selaginella | Both large and small chlorophyll grains may show evo- 
helvetica. lution of O, former when uninjured better than the 
latter, owing to their larger size. At best never more 
than 3 to 4 the activity of the evolution of O from an 
algal cell of the same size. In 15 p. e. sugar solution 
in many cases assimilation still quite distinct after 5 or 
6 hours, and in few cases still present, though much 
weaker after 10 hours, but the next morning the grains 
are always dead. In 10 p. c. sugar, the evolution of O 
is less marked, in 3 hours is very weak, and is shown 
in only few cases, in 5 hours ceases. 
In 2p. c. and 3 p. e. KNO, weak evolution of O, which 
ceases in 2-3 hours, and is present in only relatively 
very few quite uninjured grains. 
In 5 p. e. K,C,H,O,, weak evolution of O from most 
uninjured grains, but in 1-2 hours ceases. 
The evolution of oxygen very rarely approaches in strength to 
that shown by an algal cell of similar size and is nearly always 
much weaker. When the evolution of oxygen is relatively 
fairly active and the chlorophyll grain is lying free in the fluid, 
the Bacteria swarming around it may cause it to roll about or 
twist on one axis from time to time. When it is very weak, a 
Bacterium lying on or near the chlorophyll grain may be seen to 
suddenly dart off for a short distance; if the path is short it may 
return, but if long it may lose itself in the surrounding oxygenless 
desert and come to rest. This is repeated at intervals by other 
neighbouring Bacteria. 
In darkness the movement entirely stops in a minute or two, 
and on re-exposure to light is shown again almost at once, 
recommencing in less time tban it takes to cease. The stoppage 
and recommencement may be repeated many times with the 
same chlorophyll grain. Young and old, larger and smaller, 
dividing and non-dividing chlorophyll grains may show the same 
evolution of oxygen, but naturally it is more marked where the 
chlorophyll grain is larger. The fact that the evolution of 
oxygen ceases in the dark and recommences on exposure to light, 
shows that it is not due to the setting free of loosely combined 
