450 MR. A. J. EWART ON ASSIMILATORY INHIBITION. 
grains are present, though not in abundance, the green colour of 
which is often masked by a red or brown pigment. There can 
be no doubt that these plants also possess a power of assimilation 
corresponding to the amount of chlorophyll which they contain. 
Klebs * deseribes an interesting condition which may be pro- 
duced in Elodea and Funaria as the result of cultivation in a 
plasmolytie solution of sugar. This consists in a degeneration 
and, finally, complete disorganization of the chlorophyll bodies, 
the plants now being reduced to the condition of obligate para- 
sites. In Funaria the alteration appears to be due to the 
presence of a traee (005 p.e.) of K,CrO, in the solution of 
sugar employed; but in Elodea, kept in darkness in water, it 
goes on as actively as in a solution of sugar. In the sugar 
solution, according to Klebs, the change occurs more rapidly in 
light than in darkness. It consists primarily in a reduction in 
size of the chlorophyll grains, these becoming at the same time 
yellowish in colour. The degenerative changes finally convert 
the chlorophyll grains into small red dots, to which frequently 
a small starch grain is attached. From this condition no regene- 
ration appears to be possible; but if the chlorophyll grains are 
yellow or yellowish brown they may, under proper conditions, 
recover and become green and normal again. Klebs assumes 
that this degenerative change is accompanied by a loss of the 
power of assimilation, an assumption which is not justifiable 
without direct experimental proof. 
The readiest mode of causing the alteration in the chlorophyll 
grains of Elodea was found to be by keeping the plants in well 
aerated water at 30°C. and in darkness, when, after a week, 
nearly all leaves and leaf-cells remain living ; but the chlorophyll 
grains are found in all stages of degeneration from quite small 
brown grains to green and almost unmodified chlorophyll bodies. 
As soon as the chlorophyll grains begin to diminish in size and 
turn yellowish green, the power of assimilation becomes very 
weak. When they are reduced to from } to their normal size 
and have become brownish green, or brownish yellow, the leaf- 
cells lose all power of evolving oxygen on exposure to light, and 
this is naturally also the case when the grains are quite small 
and brown or brownish red. Many leaves show large patches of 
" * G. Klebs, “Beiträge zur Physiologie der Pflanzenzellen,” in Bot. Untersuch. 
Tübingen, Ed. ii. Hft. 3, 1888, p. 557. 
