THE GREEN ALGAE OF NORTH AMERICA 287 



Though this is the original species of the genus, the details 

 of development and reproduction are not as well known as in 

 the two later described species. 



4. U. PROSTRATA Gardner, 1909, p. 373, PI. XIV, figs, i 

 and 2. Frond epiphytic, the disk of 2-3 layers of cells in the 

 middle, of one layer near the margin, composed of radiating 

 filaments, free at the margin, all firmly adherent to the host ; 

 cells each with a band-shaped chromatophore and one pyrenoid, 

 6-7 fj. diam., about i diam. long near the center of the disk, in- 

 creasing to 2j/ diam. at the tips of the filaments ; terminal cell 

 blunt ; color very dark green. On Iridaea laminaroidcs Bory, 

 near San Francisco, Cal. 



Forming obscure, circular cushions, 2-3 mm. diam. on the 

 host, usually in the sterile part of the frond. The absence of 

 hairs and tapering cells would seem to justify placing this 

 species in Ulvella, but until something is known of the repro- 

 duction, there must be some uncertainty. 



13. EPICLADIA Reinke, 1888, p. 241. 



Frond microscopic, composed of filaments irregularly and 

 densely branching, forming a coating on the surface of Bryozoa ; 

 branching in one plane, when well developed taking the form 

 of a central membrane with filamentous margin ; chromatophore 

 a parietal layer with one pyrenoid. Reproduction by zoospores 

 (gametes ?) formed many in a cell, and escaping by a round 

 hole in the wall. Only one species. 



E. FLUSTRAE Reinke, 1889, p. 86; iSSga, p. 31, PI. XXIV, 

 figs. 5-9; Hazen, 1902, p. 225, PI. XLII, fig. 2 ; P. B.-A., No. 

 1 60. Cells of the central plate irregularly polygonal, usually 

 7-12 p. diam., occasionally larger ; of the free filaments short- 

 cylindrical or irregular, 5-10 p. diam. Fig. 94. Greenland to 

 N. Y. Europe. 



On the northern New England coast this plant is common in 

 spring and summer ; at New York, Hazen reports it in May, 

 but did not find it in summer and autumn. The Fuci that 

 cover the rocks in the literal zone are often overgrown with 

 Flustra, Sertularia, etc.; these are usually of a whitish or yel- 

 lowish color, but when covered by the Epidadia, they are dark 

 green ; the alga is thus easily detected. 



PRINGSHEIMIA Reinke, 1888, p. 241. 



Frond a monostromatic disk on the surface of other algae ; 

 marginal cells flat, interior cells wedge-shaped, with their 



