134 BRITISH SEA-WEEDS. 



as a striking illustration of the necessity for a naturalist 

 to be constantly on the watch. 



Order XI. SPHtEROCOCCOIDE^. 



Purple or Bed Sea-iveeds with an inarticulate, leaf-like or 

 thread-like frond, composed of many-sided or tubular cells. 

 Fructification of two hinds on different plants: — 1. Round- 

 ish or elliptical spores formed in bead-like threads, which 

 rise from a basal placenta, in conceptacles with or without 

 a terminal pore. 2. Tetraspores variously disposed. 



According to Dr. Harvey, the distinctive character of 

 this Order is the structure of the sporiferous nucleus, 

 which consists of a dense tuft of simple or branched 

 bead-like spore-threads, radiating from a cellular pla- 

 centa, fixed in the base of the cavity of an external 

 conceptacle. 



Genus LI. DELESSERIA. 



Frond rose-red, sometimes brown-red, leaf-like, branched, 

 traversed by a distinct midrib, transversely veined. Spores 

 in stalkless conceptacles, either rising from the midrib or 

 from leaflets issuing from it ; tetraspores in clusters, called 

 sori, on different parts of the frond or leaflets. — Delesseria, 

 named after M. Delessert, a distinguished botanist. 



The species of this genus are widely dispersed in the 

 northern latitudes of both hemispheres. They are re- 

 markable for their brilliant colours, large size, and ele- 

 gant form. 



Delesseria sinuosa. The sinuous Delesseria. 



Frond an oblong or obovate, deeply-cleft, toothed leaf, 

 four to six inches in length, and from one to four inches in 

 breadth, rising from a small disc-root, furnished with a 



