496 



The specimens referred to var. arctica are marked by having 

 a thick, transverse section, most commonly about 35 /<, but varying 

 from 29 /< to 45 i*. In this instance also the thailus are saccate at 

 the base and gradually divide into more or less deeply cleft seg- 

 ments of uncertain number. 



Finally, to var. intestiniformis Rosenv. I have only felt juslified 

 in referring a few single specimens from Klaksvig; they agreed 

 fairly well with Rosen vinge's description, and resembled also the 

 Greenland specimens. 



Monostroma Grevillei occurs on sheltered, but most frequently 

 on fairly exposed coasts, where it is met with near low-waler mark 

 and at half-tide level. It grows by preference in shallow hollows, 

 which contain just a little water left by the receding tide. In such 

 localities it often forms large green growths; it grows by choice 

 most usually on Corallina, but may also be found altached to other 

 algæ: Fucaceæ, etc. as well as to rocks. It is more particularly a 

 spring alga and has been observed in great abundance in April, 

 May, June and July but may also occur later on; and fruiting 

 specimens occurred in those months. It had already been found 

 by Lyngby e, as his herbarium contains a small specimen from 

 Kvivig, galhered June 9th. and cailed by him Ulva plicata (Hydrophyt., 

 p. 30) which is unquestionably this species. 



Judging from its many habitats, this species is probably coramon 

 along the coasts of the Færoes. 



168. M. undulatum Wittr. Monostr., p. 46, tab. 3, fig. 9. 



f. typica Foslie, Contrib. I, p. 114. 



/. Farlowii Foslie, 1. c. M. pulchrum Farlow New. Engl. Alg., p. 41. 



The specimens referred to the typical form agree well with 

 Foslie' s description, a transverse section of the monostromatic 

 part of the frond showing a thickness of about 20 — 56/'. 



The specimens referred to /'. Farlowii were, on the other band, 

 thinner, about 18—27// thick. They also agreed well with Foslie's 

 description and bore a fairly close resemblance to an original 

 specimen of M. pulchrum Fosl. preserved in the museum in Co- 

 penhagen. 



This species occurs littorally at half-tide level and near low- 

 water mark, or sublillorally in shallow water. It is mel with on 

 exposed coasts as well as in shellered localities, and grows some- 

 times as an epiphyte on other algæ especially Coralliua and some- 

 times directly on rocks. 



