122 COMMON SEAWEEDS. 



narrow lamina, very dark frond. The stem is eighteen 

 to twenty-four inches long, and the lamina from fifty 

 to sixty inches long. 



DESMAKESTIA. 



(Named in honour of Desmarest, a celebrated French naturalist.) 



This is a bright olive green seaweed when growing 

 in a tide-pool ; it changes to a verdigris green hue on 

 exposure to the air, when they have the peculiar pro- 

 perty of quickly decomposing other delicate seaweeds 

 with which it may come into contact ; another pecu- 

 liarity is, that fresh specimens render the paper on 

 which they are spread transparent as oil. 



Fructification unknown. 



Des]maeestia Ligulata (Strap-shaped Ligulata). 

 — Eronds from two to six feet long, edged with leaf- 

 lets ; and these leaflets are lance-shaped, with spine- 

 like teeth. The main frond has an obscure mid-rib, 

 variable in breadth, set all its length with opposite 

 branches. Young plants somewhat resemble the 

 feathered part of a quill. Frequent on the south. 

 coast of England, Jersey, Guernsey. 



Desmaeestia Actileata (Spiny Desmarestia). — 

 Eronds narrower than in the preceding specimens, 

 from one to three feet long ; the young frond, which is 

 flat, is so clothed with long silky fringes as to appear 

 as if overgrown with a parasitic Conferva. "When the 

 plant has done growing these fibres fall off, and the- 



