1919 J Setchell-Gardner : Myxophyceae 47 



gentially and are cut into two cells by a radial wall; the resulting: 

 "filaments" are of ecpial growth i\s a rule, and the forking thus 

 becomes dichotomous (pi. 3, fig. 16). Plants often become so closely 

 associated as to form a continuous layer over the surface of the host. 

 Even under this condition they have no effect upon the host, so far 

 as death and disintegration of the cells are concerned, and hence they 

 are strictly epiphytic. The erect filaments result from the horizontal 

 division of the prostrate or basal cells. They form very dense, com- 

 pact masses, their cell walls adhering firmly (pi. 3, fig. 15). The 

 gonidaiigia are numerous, spherical or slightly oval, being transformed 

 terminal cells of the erect filaments (pi. 3, fig. 14). 



2. Eadaisia subimmersa S. and G. 

 Plate 3, figs. 12, 13 



Thalli small, inconspicuous, irregular in outline on the surface of 

 the host, growing on the cuticle, or in small surface cavities ; prostrate 

 or basal layer composed of angular cells -3-5/* diam., arranged irregu- 

 larly, giving rise to erect filaments, parallel at first, later spreading 

 somewhat at the free distal ends, 35-45ju, long; cell division on the 

 free surface portion in one plane, within the host in three planes, 

 building up oval masses ; cells in erect filaments 3-5/a long, 1.5-2.5/x 

 wide, older cells frequently becoming pear-shaped ; cell contents homo- 

 geneous, blue-green ; gonidangia terminal, spherical, 4-6/t diam., pro- 

 ducing 6-8 gonidia by simultaneous division. 



Growing on Khodymenia sp. Carmel Bay, Monterey County, 

 California. The host plant was collected by Gardner (no. 3350). It is 

 a Rhodymenia and possibly R. Palmetta, at least it belongs to the 

 Palmetta group. It w^as cast ashore and slightly faded, thus making 

 the Radaism groups appear distinct, which led to their discoverj\ 

 The host is not uncommon along the California coast, and the epiphyte 

 is to be expected in other localities. 



Setchell and Gardner, in Gardner, New Pac. Coast Alg. II, 1918, 

 p. 446, pi. 37, figs. 12, 13. 



This species of Radaisia, like others, seems to be epiphytic at first 

 until the ba.sal layer of cells is produced. Plants start from a single 

 cell on the cuticle of the host, at least some of them have been so 

 observed. By repeated divisions, sometimes perpendicular to the long 

 diameter of the cell, but usually quite oblique, a single layer of cells 

 of varying shapes and sizes is built up (pi. 3, fig. 13). The cell walls 

 of this basal layer are transparent, seem to be gelatinous, so that the 



