COLOUR OF MARINE PLANTS. SD 
green as those of our graminee. “According to Bou- 
guer’s experiments, light is weakened after a pass- 
age of 192 feet, in the proportion of 1 to 1477°8. 
At the depth of 205, this fucus could only have 
had light equal to half of that supplied by a candle 
seen at the distance of a foot. The germs of several 
of the liliacee, the embryo of the mallows and other 
families, the branches of some subterranean plants, 
_and vegetables transported into mines in which the 
air contains hydrogen or a great quantity of azote, 
become green without light. From these facts one 
might be induced to think that the existence of car- 
buret of iron, which gives the green colour to the 
parenchmay of plants, is not dependent upon the 
presence of the solar rays only. Turner and many 
other botanists are of opinion that most of the sea- 
weeds which we find floating on the ocean, and 
which in certain parts of the Atlantic present the 
appearance of a vast inundated meadow, grow ori- 
ginally at the bottom of the sea, and are torn off by 
the waves. If this opinion be correct, the family 
of marine alge presents great difficulties to those 
physiologists who persist in thinking that, in all 
cases, the absence of light must produce blanching. 
The captain, having mistaken a basaltic rock for 
a castle, saluted it, and sent one of the officers to 
inquire if the English were cruising in those parts. 
Our travellers took advantage of the boat to examine 
the land, which they had regarded as a prolongation 
of the coasts of Lancerota, but which turned out 
to be the small island of La Graciosa. ‘ Nothing,” 
says Humboldt, “ can express the emotion a natu- 
ralist feels when for the first time he lands in a place 
which is not European. The attention is fixed 
B 
