THE PATH OF EVOLUTION 



possessed by chlorophyll, which enables the rapid 

 short waves of violet light to be changed into the 

 longer, slower waves of red light, is effective to the 

 same end. When the Algae are growing in the deep 

 water of the sea, so far from the sands and rocks of 

 the coast that the sandy or earthy debris thereof no 

 longer changes the pure blue tint of the deep into the 

 greenish color of the shallows, the absorption of the 

 red waves of light by the blue water is so great that 

 the chlorophyll is no longer adequate for the work re- 

 quired. Not only are the red and orange rays nearly 

 all absorbed by the water, and only the more refran- 

 gible rays, the blue and violet, transmitted, but all 

 the light rays so far lose their power that at a depth 

 of about 350 feet no light is transmitted, and at this 

 depth no plants live. In less depths, but beyond the 

 reach of the waste from the rocks and shore, grow 

 the Florideae, Algae, in which the chlorophyll is 

 masked or replaced in part by Erythrophyll, the 

 red matter of the red-colored seaweed. This sub- 

 stance, both by its own color transmitting unchanged 

 the light rays that reach the plant surface as well as by 

 its strong fluorescent properties that change the rapid- 

 ity and length of the waves of light, compensates to a 

 large extent for the deficiency of the desired red rays, 

 and facilitates the decomposition of carbon dioxide 

 and formation of the plant tissues. On the other 

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