HOW TO KNOW THE SEAWEEDS 



only be aware that he will encounter both asexual and sexual plants 

 of these groups in his collecting and that in most cases either will 

 serve equally well with regard to the use of this illustrated key. 



conceptac/e 



sporophyie 



receptacle 



macro- 

 sporantjiurri 



micro- 

 sporancjiQ. 



^oospores 

 (ant hero JO ids) 



o 



fertilisation ^ 



[aplarfospores] 



Fig. 11. Diagram of Ihe Life Cycle of Fucus. 



THE RED ALGAE . 



The elementary student of phycology has long been perplexed by 

 the problem of recognition of various kinds of red algae in the field, 

 for many of them are not really red in color, but green, brown, purple 

 or even blackish in nature. He is further discouraged when told that 

 their primary morphological distinction from other algae is found in 

 the presence of non-motile male gametes which fuse with a special 

 female sex organ, the carpogonium. It is because of such situations 

 which often make it practically impossible for a beginning student to 

 place his specimens in the right algal division that the present arti- 

 ficial key is designed to key out all groups together without regard to 

 natural relationships. 



Nevertheless, in the use of the key one will find frequent cause to 

 be acquainted with some of the fundamental aspects of reproduction 

 in the Red Algae, for in this group especially, the reproductive struc- 

 tures are often conspicuous and serve conveniently in the recognition 

 of a number of genera. 



23 



