Seaweeds and Leaf-green 
It was made to grow behind specially contrived screens 
of coloured glass, and the results were as follows :— 
Behind red glass, that is, in red light, it became green. 
9» green 9 green ss more or less red. 
» blue 5 blue 35 brownish yellow.® 
This shows that Oscillatoria is able to produce what- 
ever colour suits itself best, which is a most important 
discovery. But how is it that the wave-lengths of one 
colour set up in Oscillatoria a substance which gives 
out the vibrations of the complementary shade ? 
This is, however, an instance of what we may call a 
“fitting reaction” directly produced by the conditions 
and useful to the plant. No one, not even Maeterlinck, 
would suppose that oscillatoria had studied optics and 
intentionally manufactured the green or red, but still the 
colour is produced. 
Plant life must have commenced at some period in 
the history of the earth. There was a time when the 
world seems to have been nothing but gas and mist at 
a very high temperature. Even in such early geological 
times as that of our Coal Measures, many plants, and 
some of them very highly organised, were in full activity. 
Even then, some authors suppose that the whole ocean 
had an average surface temperature of 70° F. (21° C.), 
and that there was no cold water either in the Arctic 
or Antarctic Seas.’ 
Many alge would thrive in hot water of this tempera- 
ture. Indeed, from what we know of the endurance of 
living protoplasm, it would be very difficult to say what 
degree of heat would necessarily destroy all vegetable life. 
Even to-day algz are said to flourish and grow well 
in certain very hot springs, The water in those at 
Karlsbad is at 70° C., and in the baths at Las Trincheras, 
Venezuela, 80° C.2 Some doubt has been expressed as 
33 c 
