196 ip o s 1 e 1 s i a 



more than thirty, are the largest genera, 

 and these are also widely distributed, 

 some reaching the southern hemisphere. 

 The region of the Pacific coast of 

 North America exhibits the largest 

 number of monotypic genera, and may 

 with reason be considered as the most 

 advantageous coast in the world for 

 the study of these forms. 



Most of the kelps are very large 

 organisms, for algse, and some of them 

 are truly gigantic plants. One variety, 

 MacrocystiSy is credited with pro- 

 ducing the longest stem of any plant 

 in the world, measurements of a thou- 

 sand feet having been reported. An- 

 other type, that of Lessonia, has been 

 described by Hooker as a submarine 

 tree, and its massive trunk and hun- 

 dreds of leaf-like branches certainly 

 convey the impression of an arboreal 

 habit. The bladder kelp, Nereocystis, 



