CYCLOSPOEEJ;. 



75 



Order 1. Fucaceae. The following species are common on our 

 coasts : Fucus vesictdosus (Fig. 70) has a thallus with an entire 

 margin, and with bladders arranged in pairs ; F. serratus (Fig. 71) 

 without bladders, but with serrated margin ; Ascophyllum nodosum, 

 has strap-like shoots, which here and there are swollen to form 

 bladders ; Halidrys siliquosus has its swimming bladders divided 

 by transverse walls ; Himanthalia lorea, which is found on the west 

 coast of Norway, and the south coast of England, has a small 

 perennial, button-shaped part, from the centre of which proceeds 

 the long and sparsely branched, strap-like, annual shoot, which 



FIG. 72. Sargafsum bacciferwm. 

 portion of the thallus, natural size. 



FIG. 71. Fucus serratus. a Portion of a male plant which has been exposed to the 

 action of the open air for some time ; small orange-yellow masses, formed by the anther- 

 idia.are seen outside the mouths of the male conceptacles(nat.size). b Cross section through 

 the end of a branch of a female plant, showing the female conceptacles ( x 4). 



bears the conceptacles. The Gulf-weed (Sargassum lacciferum, 

 Fig. 72) is well known historically from the voyage of Columbus ; 

 it is met with in large, floating, detached masses in all oceans, 

 and is found most abundantly in the Atlantic, off the Canary 

 Islands and the Azores, and towards the Bermudas. The- 

 stalked, spherical air-bladders are the characteristic feature of 

 this genus. The thallus is more highly developed than in Fucus r 

 and there is a contrast between the stem and leaf-like parts. The- 



