No. 3] REMARKS ON NORTHERN LITHOTHAMNIA. 25 



and 7 — 11 fx broad. On the other hand, the perithallium in L. 

 Sonderi is nearly always more vigorously developed than in any 

 form of L. Lenormandi, but new crusts are often developed upon 

 others. The cells of the latter layer are squarish, 6 — 10//. in dia- 

 meter, or elongated vertically and about 12 p long. 



The conceptacles of sporangia in the typical form are subpro- 

 minent, rather crowded, often two or three confluent, circular or 

 nearly circular in circumference, convex or nearly disc-shaped, 

 300—500, frequently 350—400 p in diameter. In f. sublcevigata, 

 as above remarked, they are a little smaller. The roof is inter- 

 sected with 50—100 muciferous canals. It finally falls into decay, 

 and overgrown conceptacles do not occur. The sporangia are 

 four-parted, 100 — 150 p long and 35 — 60 p. broad. The concep- 

 tacles of cystocarps, occasionally occurring in the same specimens 

 as those of sporangia, are conical or subcorneal, 300 — 450 p in 

 diameter. Some smaller ones together with the latter are likely 

 to be those of antheridia, about 200 p in diameter. 



This species on one side approaches stunted forms of Lithoth. 

 Iceve, and on the other hand it is nearly related to old and uneven 

 specimens of Litlwth. Lenormandi, particularly f. subloevis. The 

 latter species and L. Sonderi are sometimes hardly distinguishable, 

 particularly when the specimens are stunted or bleached. In habit 

 the species also approaches stunted forms of Lithoth. glackde, or 

 occasionally reminds of Phymatolitlion polymorphum. 



L. Sonderi grows on rocks or stones, sometimes on shells 

 of mollusks or other calcareous algae. It frequently occurs in the 

 sublitoral region, descending to a depth of about 15 fathoms, 

 mostly, however, appearing in 4—10 fathoms. Once it has been 

 found in the lower part of the litoral region in an exposed locality 

 (f. sublcevigaia). The plant bears reproductive organs, mostly 

 sporangia, in January, March, May to August, and October. 



Area: Norway, south-west — south coast: Rovaer, f. typica, 

 f. sublcevigata (!), Haugesund(l), Mandal (Wille!,!), Fredriksvsern(!), 

 Hvaloerne(!); Sweden: Gullmarsfjord (Lagerheim, Arwidsson!); 

 Denmark (Rosenvinge!); Helgoland (Sonder, Kuckuck!); 

 Scotland, south-west coast: Bute (Mrs. Robertson!), Cumbrae 



