94 FLOWERLESS PLANTS 



explanation. It is well known that, in its 

 passage through water, the rays of sunlight 

 undergo some modification : the red, yellow, 

 and orange rays, which are so essential to the 

 green plant, are absorbed, and it is chiefly the 

 blue rays which are allowed to pass. Now, 

 owing to the peculiar pigments to be found in 

 the red seaweeds, the blue rays, of which there 

 are an abundance, even in quite deep water, 

 are changed in their character within the tissues 

 of the plants. Actually they are to an extent 

 altered into the red and orange rays, which 

 aid the green plant in the manufacture of its 

 chlorophyll. 



To a modified degree the same process is to 

 be observed in the case of the brown seaweeds, 

 which live in more shallow water than the red 

 seaweeds usually favour. Thus, although the 

 red and brown seaweeds may be living under 

 many feet of water, they are able to derive quite 

 as much benefit from the light as if the rays 

 did not have to pass through the watery screen 

 at all. It is very natural to assume that the 

 red seaweeds wiU always be found growing in 

 very deep water, the brown seaweeds in mode- 

 rate depths, and the green weeds only in the 



