87 



RED SEA-WEEDS.-RHODOSPERMEJE. 



Order VII. EHODOMELACE^. 



Bed or Brown-red or Purple Sea-weeds, with a leafy, or tkread- 

 lilee, or jointed frond composed of many-sided cells. Fruc- 

 tification of two hinds on different plants : — 1. Pear-sJiapcd 

 spores in external ovate or urn-shaped conceptacles. 2. 

 Tetraspores lodged either in distorted hranchlets or in 

 receptacles, called stiohidia. 



Genus XXXVI. ODONTHALIA. 



Frond flat, thickish, diaticliously branched, indistinctly 

 midribbed, alternately toothed at the margin. Spores in 

 marginal, stalked, egg-shaped, wide-mouthed' conceptacles ; 

 tetraspores tripartite, arranged in double rows in marginal, 

 stalked, lance-shaped stichidia. — Odonthalia, from tho 

 Greek odous, a tooth, and thalos, a branch. 



All the species of this genus are natives of cold lati- 

 tudes; one is common to the northern shores of Eu- 

 rope and Amerieaj and the remainder have only been 

 found on the north-east coasts of Asia. 



Odonthalia dentata. Toothed Odouthalia. 



Eronds rising from a hard disc, tufted, from three to 

 twelve inches high, much branched, having a midrib in the 

 lower part, and becoming flat and membranous above ; 

 branches springing from the axils of the teeth of the main, 

 stem, tapering at the base, deeply pinnatifid. Fructification 



