564 DR. A. J. EWART ON ASSIMILATORX INHIBITION. 
Experiments were also made with two water-plants, namely 
Chara and Elodea. If entire plants of Chara are kept in 
darkness, they die without becoming at all etiolated. If, however, 
the apices of strong shoots are allowed to grow into perfectly 
dark cylinders (see fig., p. 563), they may remain living for a 
considerable time. 
The following are the results thus obtained :— 
Chara fragilis—(a) After 3 weeks, the plants have three 
internodes in darkness normal in appearance, quite green, but 
paler and more transparent than the lower parts exposed to 
light. The paleness is partly due to the youth and absence of all 
deposit from the parts formed in darkness. On examination, 
the lowest branches show fairly active assimilation, the upper 
branches moderately active. (b) After 5 weeks the parts in 
darkness have increased but little in size, are green but paler 
than normal, and show moderately active evolution of O, which 
in some of the upper young branches is very weak or imper- 
ceptible. Longest stem is 5 em. (3 internodes and apical tuft). 
(c) After 8 weeks all the parts in darkness are dead. 
Hence the filaments in darkness are not supplied with suffi- 
cient food, and slowly starve. Growth becomes slower and 
slower and finally ceases, the chlorophyll pigment is formed 
in smaller quantity than normal, but no true etiolation is 
produced. In darkness Chara can produce normal green 
chloroplastids capable of fairly active assimilation. It is possible 
that ifthe supply of food-material were sufficient, the growth of 
the plant and production of new chlorophyll might go on in- 
definitely. Chara therefore in this respect resembles Pinus and 
other conifers, for here, also in the seedlings, the cotyledons 
become green in darkness, but the secondary leaves remain quite 
pale owing to the supply of food-material being insufficient in 
quantity to permit of the formation of the chlorophyll pigment 
and proper development of the chloroplastids. 
The changes undergone by the chlorophyll grains of Elodea 
when kept in darkness in water have been previously described. 
Even if the apices of vigorous shoots are led into and allowed 
to develop in dark chambers, it is very difficult to obtain etiolated 
specimens with otherwise normal chlorophyll grains, for, owing 
to the parts in darkness being subjected to partial starvation, 
the chlorophyll grains remain small, may be almost colourless, 
and such leaves developed in darkness show no power of assimil- 
ation. In November, under the mud on which the plant grows 
