108 M. FOSLIE. [1905 



posed of a solitary layer of cells except around the conceptacles, 

 frequently destitute of small cortical cells ; conceptacles of sporangia 

 and cystocarps hemispherical, 75 — 120 p. in diameter, 

 f. lacunosa Fosl. mscr. 



Descr. M. minutula 1. c. 



Syn: Lithocystis Allmanni Harv. Phyc. Brit. (1846—51), pi. 166? 



Melobesia insequilaterata Solms, Corall. Monogr. (1881), pi. 12, t. Ill, fig. 

 13—18? 



Lithothamnion (Epilithon) Van Heurckii Heydr. in Chalon, Liste Alg. Mar. 

 (1905), p. 207, fig. 1—5? 



The form of the species which I described 1. c. (the f. lacu- 

 nosa recorded above) corresponds to f. callithamnioides of M. 

 farinosa, and to a form of Lithophyllum zonale which is almost 

 similar, but young. In sterile state it is almost undistinguishable 

 from the form first mentioned. As a general rule, however, the 

 cells are smaller. It occurred sparely in the upper part of the 

 branches of Corallina officinalis, partly also on small tubes of 

 Serpula attached to Corallina, and was found at Hvaloeme on 

 the southern coast of Norway. The alga is difficult to be disco- 

 vered, particularly in sterile state, and is easily overgrown by other 

 algae, e. g. Litliophyllum macrocarpum. It forms indistinct patches, 

 not or feebly incrusted with carbonate of lime, of irregular shape, 

 lacunose or with narrower or broader shoots, now and then con- 

 sisting of a single row of cells. Sometimes the essential part of 

 the plant is composed of subdichotomous cell-rows. It is mono- 

 stromatic, except quite a small part round the conceptacles. When 

 looked on from the surface, the cells are partly squarish, 6 — \2 p 

 in diameter, partly of a length being IV4 or even IV2 of the breadth, 

 or being up to 14 p long. In a vertical section the cells are now 

 squarish, 6 — 8 p in diameter, now — and more frequently — 

 horizontally elongated, and up to about 14 p long. Small cortical 

 cells mostly seem to be wanting. The conceptacles of sporangia 

 resemble the conceptacles of antheridia in M. farinosa, and are 

 of about the same size as the latter, or 75 — 120 p in diameter, 

 with a single orifice. The sporangia are bisporic, 40 — 50 p long 

 and 20—25 p broad. The form is, therefore, easily confounded 



