40 SEAWEEDS 



great external differentiation of form and consider- 

 able internal differentiation of tissue, as well as 

 others consisting of a mere row or plate of similar 

 cells. The sub-class may be regarded as a fairly 

 natural assemblage of orders easily to be distin- 

 guished from the other sub-classes, though it includes 

 such diverse types as (1) the Fucacece, of which the 

 unciliated oospheres, many thousand times greater 

 than the antherozoids, are produced like the latter 

 in definite conceptacles, from which they are ex- 

 truded; (2) the Cutleriacece, possessing non-sexual 

 zoospores, and ciliated oospheres (or $ gametes) 

 many times larger than the antherozoids (or <J 

 gametes) the oospheres, however, being incapable 

 of fertile union until they have come to rest 

 neither borne in conceptacles ; and (3) other orders 

 possessing ciliated gametes of equal or nearly equal 

 size, in one case (Splachnidiacece) borne in con- 

 ceptacles, in the others within external mother-cells. 

 It would be doing violence to a natural system 

 of classification to accept the proposed inclusion of 

 the Diatomacece among the Phceophycece on the sole 

 ground of colour. This order is of a distinctly 

 aberrant character, and shows no morphological 

 point of contact with even the lowest groups of 

 PhceopJiycece. 



FUCACEJL 



General Characters. The distinctive characters of 

 the Fucacece are the production of unciliated 

 oospheres in oogonia and antherozoids in antheridia, 



