10 BRITISH SEA-WEEDS. 



seemingly spontaneous movements are continued for 

 some time. The vivacious granules, or zoospores, as 

 they have been called, at length become fixed to some 

 submerged object, where they soon begin to develope 

 cells, and at length grow into Algae similar to those 

 from whose cells they issued." 



The organs whose production Dr. Harvey has thus 

 lucidly described are analogous to the seeds of land 

 plants; but it is evident that, although they perform 

 the same function, they are altogether of a different 

 nature. In the descriptive part of this work they will 

 be spoken of as spores, tetraspores, antheridia, and zoo- 

 spores, and a great many important characters will be 

 found to depend on them. 



A vast amount of study has been devoted to the elu- 

 cidation of the early and obscure stages of the develop- 

 ment of Sea-weeds ; but, owing to the difficulty of con- 

 ducting observations, the results obtained are not so 

 definite as those ordinarily derived from scientific re- 

 search. Various writers do not agree as to the exact 

 nature of the different kinds of fruit, and the precise 

 part they play in Nature's drama. 



In the Olive series [Melanospermece), the fructification 

 consists wholly of spores and antheridia, which are pro- 

 duced either on the same or on separate plants. If the 

 former, it is said to be moncecioits ; if the latter, diee- 

 cious. The spores are olive-coloured, and are formed 

 from delicate, jointed fibres (paranemata) . They are 

 enveloped in a transparent membrane, called a peri- 

 spore. Each perispore contains what, in its early state, 

 appears to be a single spore; but, as this matures, it 

 either retains its individuality, or separates into two, 

 four, or eight sporules. The spores, with their peri- 



