GENERATIVE ORGANS OF FUCACE^. 



329 



look, that seems to have suggested the name of the genus (from 

 the Greek a(paxskoq, gangrene). The study of the higher and 

 larger members of this group, has recently come to present a 

 new and very attractive source of interest to the Microscopist, 

 in consequence of the discovery of the truly sexual nature of 

 their fructijfication ; and we shall take that of a common species 

 of FucuB as the type of that of the order generally. The 

 "receptacles" which are borne at the extremities of the fronds, 

 here contain both "sperm-cells" and "germ-cells;" in some 

 other species, however, they are disposed in different receptacles 

 on the same plant ; whilst in the commonest of all, F. vesiculosus 

 (bladder-wrack), they are limited to different individuals.' When 

 a section is made through 



one of the flattened recep- Fio. ii5. 



tacles of F. platyearpua, 

 its interior is seen to be a 

 nearly globular cavity (Fig. 

 115), lined with filament- 



Fig. 114. Terminal portion of branch of Sphacelaria cirrhoea. 



Fig. 115. Vertical Section of receptacle of I^us platycarpus, linecl with filaments, among which 

 lie the antheridial cells, and the sporangia containing octospbres. 



ous cells, some of which are greatly elongated, so as to project 

 through the pore by which the cavity opens on the surface. 

 Among these are to tie distinguished, towards the period of their 



' It was at first stated by MM. Thuret and Decaisne, that this species was sometimes 

 dioecious, sometimes hermaphrodite ; but they now consider the (lermaphrodite form to 

 be a distinct species, the F. platycarpus described above. 



