14 M. FOSLIE. [1905 



sely imbricate. On the other hand, it is much differing from a 

 marked f. sublcevis, which may be as good as quite even. 



As far as I know, there has not earlier been stated any 

 measure of the size of the cells in this species. A vertical radial 

 section of a part of a crust freely growing or loosely superposed 

 in the main resembles pi. VI fig. 3 by Rosanoff 1. c, but a 

 vertical section of a crust firmly adherent more resembles that of 

 Lithoth. heve, often with a hypothallium *) rather feebly developed,, 

 the convergence of the lower anticlines being feeble or wanting, 

 and the rows of the cells running upwards in rather large curves. 

 Cp. Rosenv. Gronl Havalg. fig. 7. The length of the hypothallic 

 cells is double or three times the breadth, now and then even more,, 

 the length being 1 2 — 25 or up to 32 p., the breadth being 7 — 1 1 p. 

 The perithallium is sometimes rather vigorously developed, and the 

 cells of this layer partly squarish, 6 — 9 p in diameter, partly verti- 

 cally elongated and up to 12, or now and then 16 p long. 2 ) 



The conceptacles of sporangia in f. typica are densely crowded 

 over the whole frond, except a part of the peripherical portion, 

 often so densely that the roofs become angular, now and then 

 even two or three quite confluent. They are subprominent, de- 

 pressed-hemispherical or often at length disc-shaped or nearly so^ 

 250 (200) — 350 p in diameter. In southern areas they are often 

 a little smaller than usual in northern ones. Towards maturity 

 the central portion of the roof, which is intersected with 25 — 35 

 muciferous canals, often becomes slightly concave. Before or after 

 the conceptacles are emptied the central portion of the roof is 

 gradually dissolved, the greater part of it still almost always 

 leaving a narrow prominent border. The borders contribute to 

 the uneveness of the frond, causing that the shallow or rather 

 deep scars after the conceptacles get irregularly effaced by local. 



1 ) As to the terms of the layers of tissue cf. Siboga Exp. LXI, p. 11. 



2 ) As remarked at an earlier occasion, the measures of the cells stated by 

 me in Norw. Lithoth. and in New or crit. calc. Alg. are from decalcified 



• sections, whereas in pamphlets afterwards published as well as in this one 

 the measures are from undecalcified, ground sections, which often makes 

 a considerable difference. 



