219 



This species occurs on stones and rocks, and on shells of molluscs (Miililus, 

 Modiola, Trochiis, Littorina), from ordinary water-mark to 19 meters depth. Almost 

 all the specimens belong to f. iijpica, a few only have been referred by Foslie to 

 f. sublcEvis, which differs by smoother surface and less crowded sporangial concep- 

 tacles. It was rather surprising to me to find the species growing at low-water 

 mark on the granitic rocks of Bornholm, where the salinity of the water is about 

 7— 8"/iH) only. It was here fairly typical though sterile, and with numerous adven- 

 titious fronds, and occurred in fairly great numbers. In the other locality in the 

 Baltic (RG), only sterile but rather large crusts were found. 



Ripe sporangia have been met with in July (partly together with undivided) 

 and September. Antheridial conceptacles with spermatia were found in July and 

 September, and ripe cystocarpic conceptacles in July. 



Localities. Ns: Tliyboran, groin no. 58, stunted specimens. — Lf: Sandre Ren by Lemvig; 

 Tliisted harbour (!, C. H. Ostenfeld); Sallingsund (Th. Mortensen); LS^ off Bjerndrup, east of Mors, 5,5 m. 

 — Kn: Frederilcshavn, at low-water marl?; Trindelen, 15 m (small spec). — Ke : EU, Lille Middelgrund, 

 14 m (small specim.); lA, Store Middelgrund, 16 m. — Ks: Ouro Sund; Bramsnfes Fjord. — Lb: At 

 Lyngsodde off Middelfart, 15 — 19m, large fertile crusts. — SI): GP, at Halskov Rev, 9,5 — 11,5 m; Aver- 

 nakhage by Nyborg, low water. — Sm: VC, Venegrund, 3— 5,5m. - Su: TP', Staffans Flak, 11 — 13 m; 

 PS, off Charlottenlund, 5,5 m. — Bm : RG, 6 miles N.N.W. of Falsterbo lighthouse, 11,5 m. — Bb : Hellig- 

 domsklipperne, R0, Bornholm. 



3. Lithothamnion Sonderi Hauck. 



Hauck, Meeresalgen, p. 273, Taf. Ill, fig. 5; Foslie, Norweg. Forms, 1895, p. 127; Heydrich, Lithoth. Helgol., 

 1900, p. 77, Taf. II fig. 20—22; Foslie, Remarks, 1906, p. 23; Lemoine, Structure, 1911, p. 96. 



Though this species has been met with in a number of different localities in 

 the Danish waters, it has in most cases been found only in small quantities together 

 with other species. I have therefore only little to communicate with regard to it, 

 but must refer to the descriptions of Hauck, Foslie and Mme Lemoine. 



As pointed out by Foslie and Mme Lemoine, the hypothallium is feebly devel- 

 oped. According to the last-named author it consists only of a single layer of cells; 

 "les autres se relevent tres rapidement pour former Ic perithalle". The ascending 

 filaments may, however, rise more gradually, and the hypothallium may then con- 

 sist of two or three cell-layers (fig. 136 B). The hypothallic cells measured 5—7 fj. 

 broad, 15 — 21 u long; those of the vertical filaments I found to be 3,5 -7// broad, 

 5,5 — 11 a long. These measurements are somewhat smaller than those of Foslie 

 and Mme Lemoine. Transverse fusions between the cells are very frequent in the 

 perithallium. In sections stained with hsematoxyline the middle lamellai are very 

 distinct. In the same sections the horizontal limiting lines are intensely stained; 

 their course is somewhat irregular (fig. 136). Older crusts may have a considerable 

 number of layers. The cells of the under part of the frond are often filled with 



and characterized principally by cytological statements relating to the development of the cystocarp. 

 These statements are, however, very insufficiently supported, and I have had no opportunitj' of veri- 

 fying them. 



28* 



