12 Vnivcrsiti/ of Californm Publications in Botany [Vol.8 



Schousboe, in Boriiet aud Thuret, Notes Algol., fasc. 1, 1876, p. 4. 



Pl^conm is a geuus of three known species founded on P. vesiculosa 

 Schousb. from "Tingin" on the coast of Morocco. There are now 

 three kno\\Ti species, one of whieli (P. africana Wille) is an inhab- 

 itant of fresh water while P. vcsi-culosa Schousb. and P. violacea S. and 

 G. are marine. M. A. Howe (1914, p. 11) has indicated the presence 

 of a species on the coast of Peru, but has not assigned to it any definite 

 specific name. 



Placoma is closely related to EntopJiysalis, Oncohijrsa and Chon- 

 drocystis. From Eniophysalis, it differs in its more hemispherical 

 type of thallus, from Oncohyrsa in its less strictly and regularlj^ radi- 

 ating rows of cells, while from Chrondrocystis, it differs in the pos- 

 session of Gloeocapsoid teguments enveloping the cells. 



Placoma violacea S. and G. 



Plate 4, fig-. 1 



Thallus microscopic, 175-250/a diam., irregular to somewhat 

 spherical, verrucose, tegument pale violet ; cells 3.5-4/a diam., in groups 

 of 2-8, usually of 4, mostly without order in the interior, but arranged 

 radialh' toward the periphery, angular when young, becoming spher- 

 ical later, special teguments very distinct and violet toward the sur- 

 face, hyaline below; protoplast homogeneous, pale blue-green. 



Forming a sort of pulverulent or verrucose black layer, intermixed 

 with other Myxophj'ceae, on logs along high water mark. Cape 

 Flattery, Washington. 



Setchell and Gardner, in Gardner, New Pac. Coast Alg. Ill, 1918a, 

 p. 456. 



Placoma violacea resembles P. africana Wille (1903, p. 90), a fresh 

 water species from South Africa. Besides the difference in habitat, 

 P. violacea has larger cells, aggregated into larger colonies, and pos- 

 sesses a violet colored tegument. 



6. Anacystis ]\Ienegh. 



Cells spherical to oval, with very thin cell walls and blue-green or 

 violet protoplast, associated into small spherical or' more or less lobed 

 and irregular colonies, and embedded within a copious gelatinous 

 tegument, within which they are either uniformly distributed or seg- 

 regated in small groups ; cell divisions in all planes. 



