FUCACE.S 



235 



duction consisting in the impregnation of a passive oosphere by motile 

 antherozoids attains its highest development among Alg». The 

 antherozoids retain their motility and vitality for from one to three days. 

 The oospheres will show signs of a rudimentary germination even when 

 unfertilised, but in that case the germ soon perishes. Thuret succeeded 

 in obtaining a hybrid Fucus by impregnating the oospheres of F. vesicu- 

 losus (L.) by the antherozoids of F. serratus (L.). 



A short time after impregnation the oosperm invests itself with a 

 cell-wall, fixes itself to some other body, and begins to germinate with- 

 out any intervening period of rest. The first transverse division of 

 the young germinating filament is followed by others in various direc- 

 tions, so that a solid 

 mass of pseudo- 

 parenchyme is at 

 length formed, fixed 

 to the bottom by a 

 root-like rhizoid. 



The Fucaceae 

 constitute a small 

 and well - marked 

 family of seaweeds, 

 united by some sys- 

 tematists with the 

 PhaeosporeEe, or at 

 least with the Lami- 

 nariaces, to make 

 up the Fucoideffi 

 of Agardh, or the 

 Melanospermeae of 

 Harvey. They are, 

 however, well dis- 

 tinguished by their 

 mode of reproduc- 

 tion. The family 

 is represented in 

 Britain by the genera 

 Halidrys (Grev.), 

 Cystosira (Ag.), Pycnophycus (Ktz.), Fucus (L.), Ascophylla (Stackh.), and 

 Himanthalia (Lyng.), and includes also the exotic genera Sargassum (Ag.), 

 Pelvetia (Dene.), Durvillsea(Bory), Splachnidium(Grev.), and a few others. 

 Although the number of native British species described by Harvey is only 

 thirteen, some of these occur in such vast quantities that the Fucaceae 



Fig. 211.— The gulfweed, Sargassuvi lacciferum Ag. 

 (natural size). 



