14 



sometimes approach L. varians f. verrucosa in habit and may 

 be even difficult to separate in a sterile state. On the other side 

 it passes into the form torosa, in which the crust and lobes bear 

 more or less subhemispherical, smaller or larger processes, in some 

 respects corresponding with the form irregulare of L. varians, 

 being, however, a much larger and coarser plant than the latter. 

 At Kjelmo in East-Finmarken I also met with a form, in which 

 the simple branches are rather thicker than in the typical one 

 carrying more or less numerous wart-like processes, and now and 

 then even forming bundles, in all most closely related to the named 

 form. I, however, did not succeed in finding the sporangia, but 

 the conceptacles fully resemble those in L. glaciale. Cp. pi. 2, 

 fig. 2, a specimen anastomosed with L. breviaxe. The species is, 

 in the Arctic Sea, one of the largest of the genus, attaining a dia- 

 meter of at least 0.5 m. 



The conceptacles of sporangia frequently are, in the specimens 

 that I have seen, somewhat larger than those quoted by Kj ell man 

 1. c, or the circular or oblong and convex roof up to 400 /*, most 

 frequently about 300 — 350 fx in diameter. It is intersected with 

 50 — 70 canals, which are crowded in the middle of the roof. After 

 the central or greater portion of the roof is nearly dissolved, this 

 portion often gets somewhat depressed, and then it looks, in a 

 certain stage, as if the conceptacles were surrounded by an annular 

 border. Sometimes the whole roof falls away, and the scar be- 

 comes effaced by a local formation of tissue. The sporangia ap- 

 pear to be much varying in size. I found them up to 180 ji long 

 and 80 [i broad. Cp. Kjellm. 1. c. 



I have not seen cystocarpic conceptacles in typical specimens 

 of this species, but some few ones found in a form apparently 

 referrible to f. typica are conical, low and about 400 ^ in diameter 

 at the base. Some other conceptacles are about 250 — 300 p. in 

 diameter at the base, probably antheridian ones, and in shape 

 agreeing with the former. 



Relation to other species. The present plant is a true hyper- 

 borean Lithothamnion, that has probably originated within the Arctic 

 Sea, and not unlikely more species have issued from it and been 



