THE GREEN ALGAE OF NORTH AMERICA 357 



cell division general, cells other than terminal usually short ; 

 special descending rhizoidal branches, or special spine-like or 

 hooked branches present, more or less matting the tufts to- 

 gether ; cells in one species uninucleate. Otherwise as in Cla- 

 dophora. Marine. 



The special branches give this genus a higher rank than that 

 of Cladophora, and the predominance of intercalary cell division 

 also distinguishes it. The species are most abundant in arctic 

 waters, not extending south beyond the temperate zone. The 

 species from the Atlantic here included in Spongomorpha would 

 be placed by Scandinavian authors under Acrosiphonia, follow- 

 ing the monograph of that genus by Kjellman, 1893, except that 

 if Wille, iSgga, is followed, the multinucleate species are in- 

 cluded in Acrosiphonia, and Spongomorpha is used only for the 

 uninucleate Cladophora lanosa. In Jonsson, 1904, the algae of 

 East Greenland are thus divided, but the old specific names 

 arcta and lanosa disappear entirely, Acrosiphonia incurva and 

 Spongomorpha vernal is appearing instead. It is hard to see 

 what principle justifies this. Spongomorpha dates to Kiitzing, 

 1843; Acrosiphonia to J. G. Agardh, 1846; the specific names 

 incurva and vcrnalis are of Kjellman, 1893, while arcta dates 

 from Dillwyn, 1809, and lanosa from Roth, 1806. 



KEY TO THE SPECIES OF SPONGOMORPHA. 



i. Spinous or hooked branches present. 2. 



i. Spinous or hooked branches wanting. 4. 



i 2. Branches not spinous ; tufts little matted. i. S. duriitsciila. 



2. Branches spinous ; mature tufts densely matted. 3. 



3. Filaments 100 /j. diam. at tip. 6. S. spinescens. 



3. Filaments 200 i*. diam. at tip. 7- S. coalita. 



4. Filaments 200-500 fj. diam. at tip. 2. 5". hystrix. 



4. Filaments less than 150 /u diam. at tip. 5- 



5. Main filaments and branches obtuse. 6. 



5. Main filaments and branches blunt-pointed. 5. S. saxatilis. 



6. Filaments 30-40 /m diam. 3- $" lanosa. 



6. Filaments 60-100 /j. diam. 4- S. arcta. 



i. S. duriuscula (Rupr.) nov. comb. ; Cladophora alaskana 

 Collins in Setchell and Gardner, 1903, p. 228; P. B.-A., No. 

 917. Tufts 15-25 cm. high, erect, main filaments firm, straight, 

 with thick, striate walls, 200-250 /u, diam. below, 300 at tip; 

 articulations >2-i>2 diam. long, 2-3 diam. at the blunt tips; 

 branches similar, erect, scattered or in secund series of two or 



