THE ALGM 189 



although when germinating alone they are said to produce 

 weaker plants than those formed as the result of con- 

 jugation. Otherwise there is no difference between the 

 products of sexual and asexual reproduction, for the 

 zygospore, like the solitary zoospore, gives rise directly to 

 a plant like the parent. 1 



In some localities germination without previous con- 

 jugation appears to be the rule. It is only in very few 

 species that anything like a sexual process has been 

 observed in Phseophycese. In the vast majority of the 

 forms, such knowledge as we have goes to show that the 

 motile cells, whether derived from unilocular or pluri- 

 locular sporangia, are simply zoosporei capable of directly 

 reproducing the plant. There is need for much further 

 observation before we have anything like a satisfactory 

 idea of the propagation and life-history of these plants. 

 The sporangia and zoospores are very uniform throughout 

 the Phaeozoosporeae, but in the vegetive structure there 

 is the greatest variation. We have chosen one of the 

 simplest examples. In other families of the group, as the 

 oarweeds (Laminarice) and their allies, the thallus attains 

 a vast size, and becomes extremely complex in anatomical 

 structure. 



TYPE XV. PELVETIA CANALICULATA 



Among the commonest and most conspicuous seaweeds 

 on the coasts of cold and temperate countries are the 

 members of the order Fucacece. The species chosen for 

 our type is distinguished from all others on our shores 

 by the position in which it grows, which is always close 



1 It is fair to mention that some doubt has recently been cast on the 

 alleged sexual reproduction of Ectocarpus, 



