FUCUS SK1UIATUS 391 





PILEOPHYCE.E 

 FUCUS SERRATUS, L. (Wrack) 



OBSERVATIONS WITH THE NAKED EYE 



I. Of the various species of Fucus which are to be 

 found on our shores, the best adapted for laboratory 

 work is Fucu-s serratus : it is to be found near or below 

 mid-tide level, and may be distinguished from other 

 species by its dark olive colour, the flattened form 

 and serrate margin of the branches of the thai 1 us, the 

 absence of swollen <; bladders," and the presence of 

 numerous dot-like conceptacles, crowded together on 

 the ends of branches which show no special swelling. 



Having recognized the species by these characters, 

 examine a well-developed plant with the naked eye, 

 and note that the thallus as a whole shows no differ- 

 entiation of stem, leaf, and root, as in vascular plants ; 

 it consists of the following parts 



1. The flattened disk, of irregular outline, by means 

 of which the plant is firmly attached to the substratum : 

 the attachment is at times so firm that the stalk itself 

 will break before the attachment gives way. 



2. The stalk, which in old plants is of compressed 

 cylindrical form, but in young plants it may be clearly 

 seen that it is originally a broad flattened expansion, 

 with a more or less thickened midrib: a comparison 



