Myxophyceae 49 



Borgesen and Jonsson. The Distribution of the Marine Algae of the 

 Arctic Sea and of the northernmost part of the Atlantic. Bot. Faeroes. 

 App. XXV. 190S. 



Plate III. fig. 4- 



Colonies 45 mic. or more in diameter, somewhat spherical or hemi- 

 spherical, dark violet in color; cells 10-13 rnic. in diameter, hemispherical, 

 angular, depressed or somewhat spherical, at first solitary afterwards aggre- 

 gated; gonidia 1-2 mic. in diameter. 



Greenland. On the stirface of Rhizoclonium riparium val- 

 idum. Littoral zone. Fiskernas. (Rosenvinge). East and west portions. 

 (Borgesen and Jonsson). 



111. Pleurocapsa crepidinum Collins. Notes on Algae. III. Rhodora. 



136. igoi. De Toni. Syll. Algar. 5: 121. 1907. 



Collins, Holden and Setchell. Phyc. Bor.-Am. Fasc. 24. no. 1157. 1904. 



Cells up to 15 mic. in diameter, spherical or by mutual pressure polyg- 

 onal, often remaining attached in dense masses after dividing; cell con- 

 tents dull blue or slate color; gonidangia spherical, filled with small go- 

 nidia. 



Maine. Occurring sparingly in a coating composed of several minute 

 algae, on the woodwork of an old wharf. Otter Creek, Mount Desert. July 

 1900. (Collins). Massachusetts. On Balani and rocks. Magnolia Point. 

 September 1903. (Farlow). 



Genus XENOCOCCUS Thuret. Ann. Sci. Nat. Bot. VI. i: 6. 1875. 



Colonies disc-shaped or crustaceous, attached; cells somewhat spherical, 

 or angular with rounded apices, crowded, forming a parenchymatous, one- 

 celled layer, later several cells in thickness; tegument colorless or yellow- 

 ish; cell contents homogeneous, blue-green or violet; reproduction by cell 

 division in three directions or by means of gonidia developed in large 

 peripheral cells; gonidia usually spherical, sometimes 32 developed in a 

 gonidangium. 



I Colonies disc-shaped, composed of one layer of cells; tegument sur- 

 rounding base of cells; cells 3-4 mic. in diameter, 5.5-7 mic. long, pear- 

 shaped. X. laysanensis 



II Colonies spherical, solitary or confluent and completely surrounding 

 the filaments of the host; cells 4-9 mic. in diameter, spherical or flattened. 



X. schousboei 



III Colonies irregularly expanded, one or several layers in thickness; 

 cells 4-6 mic. in diameter, 4-9 mic. in length. X. kerneri 



112. Xenococcus laysanensis Lemmermann Algenfl. Sandwich-Inseln. Bot. 



Jahrb. 34: 618. pi. 8. f. 11-12. 1905. De Toni. Syll. Algar. 5: 134. 

 1907. 



Plate III. fig. 5, 6. 



Colonies epiphytic, disc-shaped, pseudo-parenchymatous, composed of 



