233 



only a feeble trace of deepening or elevation (fig. 150 C). The roof is sometimes 

 convex, though inserted in the bottom of a hollow. The sporangia are, as stated 

 by FosLiE, always two-spored. I found them to be 95 — 126// long, (18 — )37 — 53 « 

 broad, thus a little smaller than the dimensions found by Foslie, which might 

 perhaps partly be caused 

 by the fact that my mea- 

 surements have mostly 

 been made with dehydra- 

 ted sections. The concep- 

 tacles are sometimes co- 

 vered by a particular tissue 

 similar to that mentioned 

 for L. poly morphum (p. 230). 

 It has also been mentioned 

 by Heydrich and Foslie 

 (Remarks, p. 80). Accor- 

 ding to the first named 

 author (1. c. p. 76) it is al- 

 ways present in L. em- 

 boloides which, as shown 

 by Foslie, is identical 

 with L. Icevigatum; it is, however, not suitable for use as a specific character, for in 

 some specimens it covers all or nearly all the conceptacles, while in others it is 

 almost or entirely wanting. I have only seen it on emptied conceptacles which 

 still showed muciferous canals (fig. 151 C). It has a white colour. 



After the evacuation of the sporangia, the roof falls into decay. A regenera- 

 ting tissue, produced from the bottom of the conceptacle, consisting of ascending 

 filaments, may then fill the empty cavity. A new conceptacle is frequently produ- 

 ced at so small distance over the first one that the base of the second is situated 

 within the limit of the first, and the new one is thus partly produced by the re- 

 generating tissue (fig. 150, 151). Overgrown empty conceptacles do not occur. 



The species occurs in depths of 2 — 24,5 m, most frequently 5 — 20 m, growing 

 on stones and on Mytilm and Ostrea, often in company with other Lithothamnia, 

 as L. Lenorinandi, L. glaciale and L. polyinorphum. It has been found growing over 

 L. glaciale, and in one case on the frond of Chondrus ciispus. It has been found 

 with ripe sporangia in April and May. 



Localities. Ns : aF, N.W. of Thyboran, .31 m. — Sk: 4 miles N.V^E- of Svinklarv beacon. 9 m 

 (A. C. Johansen); SY off Lokken, 13 m; ZK«, off Ler.strup, 12 m; off Hirshals (Bergesen). - Lf: Salling- 

 sund near Nykobing (Tli. Morteiisen, !); LS\ 5,5 m and aT', 4 — 5 m, east of Mors; Livo Bredning iC. H. 

 Ostenfeld); Lendrup Ron. — Kii: Herthas Flak, 19 — 22 m; east of Deget near Frederikshavn; Trindelen, 

 near the double broom (Bargesen). — Ke : IL, Fladen, 24,5 m ; 00, Saborg Hoved Grund, 8,5 m. — Ks: 

 RL, north of Gilleleje, 15 m; HO, N.W. of Gilleleje, 22,5 m; OS, Hastens Grund, 14 m. — Sa : KM, east 

 of 0reflippen; BE, off Sletterhage; YV, east of Samsa, 15 m; north side of RefsniES, 19 m (C. H. Ostenfeld); 



U. K. U. Vuleiisk. Selsk. Skr., 7. Rn.>kke, iiaturvideiisk. og matliem. Afil. VU. 2, 30 



c 



Fig. 151. 



Lithothamnion Iceuigatum. A, vertical section of hypothalliuni and tlie under 

 part of perithallium. B, vertical section of crust with emptied sporangial con- 

 ceptacle filled with regenerative tissue, sliowing tlie outlines ot older tilled 

 conceptacles C, vertical section of empty conceptacle with covering tissue. 

 A 350:1. B -C(55:l. 



