70 SEAWEEDS 



ptcris Mertcnsii and Haplospora globosa have been 

 found in British seas at Cumbrae in the Clyde Sea 

 area. 



SPLACHNIDIACE^E. 



General Characters. The only reproductive organs 

 known in this monotypic order are zoospores con- 

 tained in sporangia borne within conceptacles 

 resembling in appearance those of the Fucaccce, but 

 originating in a different manner. The sporangia 

 are unilocular and resemble very closely those of the 

 Laminariacem. The zoospores presumably germinate 

 without conjugation, like the zoospores of other 

 unilocular sporangia in the Phwophycccc, but no 

 observations have as yet been made. The thallus, 

 which is of considerable stature, is attached to the 

 substratum by a disc, and consists externally of 

 parenchymatous cells, and internally of threads 

 traversing a ropy mucous mass. It grows by means 

 of an apical meristem. Only one species is known, 

 viz. Splachnidium rugosum Grev. 



The Thallus. Plants of Splachnidium rugosumvsiYy 

 from about four inches to a foot in height, and spring 

 in five or six separate fronds from a common disc. Each 

 frond is of cylindrical form, tapering downwards and 

 ending bluntly upwards, while giving off irregularly 

 smaller branches of similar form. It is marked by 

 numerous pits containing hairs, and at a later stage 

 sporangia. The outer wall consists of two layers of 

 epidermal cells, small and approximately cubical in 

 shape, and three layers of cortical cells, at first poly- 



