108 MELOBESIA. 



frond, and containing a tuft of transversely parted, oblong 

 tetraspores. Named from one of the sea-nymphs of Hesiod. 



* Frond thick, solid, stony, either shrub-like or encrusting. 



1. M. polymorpha, Linn.; frond attached to rocks, thick, 

 stony, encrusting, or rising into short, clumsy branches, which 

 are seldom much divided, and often merely rudimentary. 



On rocks, stones, shells, &c. between tide-marks. Perennial. Common. 

 I suppose that most of the thick, difform, nulliporous crusts found between 

 tide-marks would be referable to this species. Much remains to be done 

 in working out the species of this genus. I do not pretend to understand 

 them fully, not having sufficiently attended to their variations on the coast, 

 and not possessing a sufficient suite of specimens to enable me to solve 

 their difficulties in the cabinet. 



2. M. calcarea, Ell. and Sol. ; " is extremely white, solid 

 and dichotomously branched ; the little branches often unite 

 together and become smaller at the ends." Ellis and Sol. 

 p. 129, t. 23, /. 13 : Johnst. Brit. Lith. p. 240, t. 24, /. 4, 

 5. M.fragilis, M'Calla? 



Coasts of South of England and West of Scotland and Ireland. I have 

 not seen any authentic specimen, but Ellis's figure is a faithful representa- 

 tion of the M.fragilis of M'Calla, which abounds on most of our coasts in 

 4 10 fathoms water. When recent it is a deep blood red, soon passing 

 into brick-dust colour, and finally to a snowy whiteness. The branches 

 are slender, divaricating, spreading in all directions, anastomosing below ; 

 free above and tapering to a blunt point. The ultimate ramuli are either 

 simple or forked. On many parts of the coast this plant forms vast beds, 

 extending for miles, in submarine strata ; and is advantageously used as a 

 manure on soils requiring the addition of lime. Here should also be men- 

 tioned M. compressa of M'Calla, which I have not yet had an opportunity 

 of examining in a recent state. It differs from M. calcarea in having a 

 compressed frond, with flat branches broader towards the tips, and is pro- 

 bably as good a species as any other of these variable forms. 



3. M. fasciculata, Lam. ; frond unattached, roundish or 

 lobed, stony, much branched, fastigiate; branches solid, 

 thick, crowded together, cylindrical or compressed ; apices 

 truncate, broad, somewhat concave. Johnst. Brit. Lith. p. 

 240 ; Harv. Phyc. Brit. t. Ixxiv. 



Lying at the sandy bottom of the sea in 4 5 fathoms water. Found on 

 several parts of the coast. Fronds 1 3 inches in diameter, roundish or 

 irregularly lobed, composed of a stony central mass, from which issue seve- 

 ral short lumpy branches. Colour a dark lurid purple, soon fading in 

 the air. 



** Frond thin, foliated, free, or partially attached to rocks. 



4. M. agariciformit, Pall.; frond unattached, globular, 



