360 



Fani. Cladophoracese. 



I'rospora mirabilis Arescli. , Rosenv. Grl. Havalg. p. 918. fig. 35, 

 Deux. Mem. p. 106. 



This species is exceedingly common along the coasts of Iceland and 

 occurs gregariously on stones and rocks at high- water mark. It often 

 forms widely expanded strata in company with Ulothrix flacca and Mono- 

 stroma groenlandicum. Fructiferous specimens have been collected in 

 May — September. 



The specimens I have referred to the typical form consist for the 

 most part of short cells, about as long as broad or twice as long as 

 broad, and the sporangia are usually tumid, but filaments containing 

 both elongated cells, more than twice as long as broad, and short cells, 

 having cylindric or almost cylindric sporangia also occur. The sterile 

 filaments are 20 — 50 fi thick, fructiferous filaments 23 — 72 fi thick. 

 The filaments are usually somewhat narrower below than above, 

 sometimes the upper and the lower part are of about the same thickness 

 but I have not seldom met with filaments about two times thicker above 

 than below. 



The plants, which I have referred to the f. elongata Rosenv. (Grl. 

 Havalg. p. 918) have for the most part elongated cells, up to five times 

 longer than broad, and cylindric or almost cylindric sporangia, but fila- 

 ments, which besides elongated cells also contain shorter cells, about as 

 long as broad, and tumid sporangia, are also occurring. The filaments 

 are 40—65// thick. 



Urospora mirabilis has, according to Kjellman (Blastophysa och Uro- 

 spora p. 13, fig. 14 — 15) and Borgesen (Faer. alg. p. 500, fig. 100), besides 

 extramatrical rhizoids at the base, intramatrical rhizoids resembling those 

 of Chaetomorpha described by Rosenvinge (Gladophora og Chtetomorpha 

 p. 24 — 29). 1 have also in my material met with both extramatrical 

 and intramatrical rhizoids , but as a great deal of my plants were 

 destitute of the base, I do not know, whether the intramatrical rhizoids 

 are to be regarded as normally occurring in the Icelandic specimens 

 or not. 



The membrane of Urospora mirabilis is, as pointed out by Rosen- 

 vinge (Grl. Havalg. I.e.) and Kjellman (Blastophysa och Urospora p. 12), 

 indistinctly lamellate, and I have found it consisting internally of a pro- 

 . portionally thick layer of cellulose and externally of a proportionally thin 

 layer of pectose, in which respect Urospora mirabilis fully agrees with 

 Urospora Hartzii and differs from Urospora Wormskioldii. 



