60 Plant Life and Evolution 



Giant Kelps. The former is a most striking sea- 

 weed of the Northern Pacific Coast, where it is said 

 to reach a length of one hundred meters. Its slen- 

 der stem is firmly anchored in deep water, reaching 

 to the surface, where it expands a cluster of broad 

 leaves two or three meters in length, and buoyed 

 up by a great bladder-like float as big as a croquet 

 ball. Macrocystis is said to reach even a greater 

 length than Nereocystis, and great beds of this kelp 

 occur off the California Coast. These beds of kelp, 

 as for instance at Santa Barbara, form very efficient 

 breakwaters. 



Some of the kelps, like the curious sea-palm 

 (Postelsia) (Fig. 20), are specially adapted to 

 growth in the heaviest surf, and seek the most ex- 

 posed rocks, where they are subjected to the full 

 force of the great Pacific rollers. 



Gulf Weed. Other striking types of the brown 

 algae are the floating forms like the gulf-weed 

 (Sargassum) of the Caribbean Sea, which is drifted 

 northward by the Gulf Stream and is familiar 

 enough to transatlantic voyagers. Many similar 

 forms occur in the warmer seas, and they are espe- 

 cially abundant off the coast of Japan. It is still 

 not settled whether all of these floating species begin 

 life as attached plants, and are subsequently torn 

 from their moorings. That they live for a very 

 long time in the floating condition is shown 

 by the long distances from land at which they 

 occur, in a vigorously growing condition. Some- 



