DictyoteccP^ choeda. 151 



Genus XXY. CHOEDA, Stacl-Jioiise. 



Gen. Char. Root scutate. Frond simple, cylindrical, tubular, 

 its cavity divided by transverse, membranous septa, into separate 

 chambers. Fructification, a stratum of obconical spores, much 

 attenuated at the base, covering the whole external surface of 

 the frond. Among these are found elliptical antheridia ? — The 

 name signifies a cord. — Harvey. 



1. Chouda ?iluMj Lamoiir. (Plate III. fig. 9.) 

 Hab. In tlie sea, on rocks and stones, very common. 

 Annual? Summer, autumn, and winter. 



The structure of this Algee, which seems cylindrical, is 

 very remarkable, being composed of a fillet spirally twisted 

 into a filiform tube. The colour is olive-green, becoming 

 dark in drying. It is clothed with pellucid hair-like fibres, 

 which, with the mucus of the plant, give it a slippery feel. 

 The length to which it grows in favourable circumstance> 

 is very great, even thirt}^, and at times forty feet. Like 

 Sargassum, it forms at some places extensive sea-meadows ; 

 but, though floating, it is always under the surface. Dr. 

 Patrick Neill says : " In Orkney we have sailed through 

 meadows of it in a pinnace, not without some difficulty, 

 where the water was between three and four fathoms deep, 

 and where, of course, the waving weed must have been 



