CYCLOSPORE^:. 



75 



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

 coasts : Fucus vesiculosus (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 ; Ascophijllum nodosiim 

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

 bladders ; Halidrys siliquosus has its swimming bladders divided 

 by transverse walls; Himanthalia Zorea, 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 baccifernm. A 

 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 cnneeptacles (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 (Sargassiim bacciferum, 

 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, 

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



