(122) 



_..,^ ■ / subcoriaceous, scarcely adhering to paper. Colour, a dark olivaceous 

 .'; .' ' ' Timber brown. 



'This curious plant is by no means xmfrequent on most of our shores, 

 , ,'/ ■ '• -and is particularly abundant and luxuriant on the west coast, spread- 

 ing Qver the surface of rocks, often to a considerable extent ; the fronds 

 frequently more or less confluent and irregular, and often arising into 

 rough corrugated excrescences by compression, not unlike in appearance 

 some of the subfoliaceous lichens, but of a dark brown colour, and 

 possessing a very different structure from that of any lichen. 



In external form, this bears a close resemblance to Peisonellia, Hilden- 

 hrandtia, and Cruoria, and to the two former even in structui'e, but 

 the colour and the structure of the spores are very different. 



It is perhaps one of the least beautiful or attractive of the Algae, 

 either externally or microscopically ; a thin slice, however, of the tubercles 

 composing the fructification is an object of considerable interest, espe- 

 cially when contrasted with the rugged and amorphous appearance of 

 the plant which produces it. 



RALPSIA VERRUCOSA. 



EXPLANATION OF DISSECTIONS, &c. 



Fig. 1. — Ralfsia verrucosa, natural size. 

 2. — Vertical section of same. 

 3. — Cells or filaments of the frond. 

 4. — Filaments of the tubercles and spore. All magnified. 



