RHODYMENIACEiE. 167 



This genus formerly included a large number of plants, 

 which resembled each other in habit and other respects, 

 but which more accurate observation has shown to be 

 very widely separated by difference of structure. Pro- 

 fessor Agardh has reduced the species to about a dozen 

 at most, and only two of these are British; even this 

 curtailed genus is divided into two sections, each of 

 which contains one of our species. 



Rhodymenia palmata. The hand-shaped Rhody- 

 menia. 



Fronds from a few inches to more than a foot long, and 

 often nearly as wide, wedge-shaped at the base, irregularly 

 cleft in a forked or palmate manner; the margin generally flat, 

 but sometimes furnished with small leaflets, which give the 

 frond a pinnate appearance; substance membranaceous, 

 becoming tough and leathery with age. Hoot a small disc. 

 Tetraspores distributed over the whole frond, in cloud-like 

 spots. 



This plant assumes so many varied forms, either from 

 peculiar conditions of growth, from age, or from mere 

 caprice, that it would be wasted labour to attempt to 

 describe them all. They are best studied in Nature's 

 boundless schoolroom among the rocks, and in order to 

 impress them on the mind it is desirable to collect as 

 complete and varied a series of specimens as circum- 

 stances may permit. The following forms are, perhaps, 

 worthy of brief notice : — 



Var. /3. marginifera. Frond with leaflets on its 

 margin. 



Var. 7. simplex. Frond undivided, wedge-shaped. 



Var. 8. Sarniensis. Frond divided into linear seg- 

 ments. 



