442 BULLETIN OF THE BUREAU OF FISHERIES. 



Genus 3. Phaeostroma Kuckuck. 

 Phaeostroma. Kuckuck, in Reinbold. 1893. P- 43- 



Thallus composed of a small disk, usually monostromatic, consisting of radiating, 

 branched, coalescent filaments, furnished with hairs arising by basal growth; both 

 "unilocular" and " plurilocular " sporangia arising from the transformation of vege- 

 tative cells, rather prominent; "unilocular sporangia" globose or pear-shaped, opening 

 by an apical cleft, "plurilocular sporangia" irregularly rounded or nodule-shaped. 



Five species described, four of these from the northern shores of Europe. The 

 genus has not previously been recorded from North America, except Greenland. 



This genus, usually placed among the Encoeliaceae, has seemed to the author, from 

 the vegetative structure and from the mode of formation of the reproductive organs, 

 more nearly related to the Ectocarpaceae, and has accordingly been placed there. 

 Phseostroma pusillum Howe and Hoyt. PI. CXV, figs. 1-9. 



Phteostroma pusittum, Howe and Hoyt, 1916, p. 109, pi. n, figs. 1-9. 



Thallus composed of horizontal branching filaments, forming irregular or somewhat disk-shaped 

 patches, 0.3 to 0.8 mm. in diameter, closely attached to the surface of the host, usually consisting of a 

 single, moderately compact layer with irregular margins; vegetative cells somewhat cylindrical or more 

 often curved or of irregular diameter, mostly 10 to 16 mic. by 5 to 10 mic., usually 1.5 to 2 times as long 

 as broad; hairs occasional, 8 to 10 mic. in diameter, showing at the base 4 to 6 short cells (5 to 10 mic. 

 long); "unilocular" and "plurilocular sporangia" borne on separate individuals; "unilocular spo- 

 rangia" either (i) scattered or aggregated, obovoid or somewhat globose, 8 to 16 mic. in diameter, sessile, 

 or, (2) by subdivision and branching of the fundamental cell and by coalescence, forming elevated, 

 submoriform sori 16 to 48 mic. in diameter, the ultimate sporangia then smaller, mostly 5 to 8 mic. in 

 diameter, and often more angular; "plurilocular sporangia" scattered and solitary or forming loose 

 clusters, ovoid, ellipsoid, or subconic, sessile, rather erect, 22 to 27 mic. by 15 to 18 mic. 



Endemic. 



Fairly abundant on Dictyota dichotoma and the creeping stolons of Campanularian hydroids on 

 this, and occasionally on Spyridia sp., from the coral reef offshore, Beaufort, N. C., August, 1914. 



This species occurs on the Dictyota mixed with other filamentous species, but is easily distinguished 

 from them by the descriptions and figures. It is not likely to be mistaken for any other species occurring 

 in this region. It is not known elsewhere. 



Family 2. ENCCELIACE^E (Kuetzing) Kjellman. 



Frond extremely various in size and form, usually narrowed to a stipe below, 

 attached by a rootlike disk or by rhizoids, usually simple, occasionally sparsely branched; 

 structure parenchymatous; longitudinal growth intercalary, usually continuing longest 

 in the lower part; both "unilocular" and "plurilocular" sporangia formed by the 

 transformation of superficial cells or segments of these cells, external or immersed, 

 occurring singly or grouped in sori, often accompanied by paraphyses; products of 

 sporangia imperfectly known; in some cases isogametes, formed in "plurilocular spo- 

 rangia," fuse to form a zygote ; in other cases fusion of gametes apparently is not necessary 

 for their development. 



About 35 species, in all seas. 



KEY TO GENERA. 



Paraphyses lacking ; sporangia, at least in the beginning, bound together into a tissuelike mass; 



frond band or leaf shaped i. Petalonia (p. 443). 



Paraphyses present or lacking ; frond filiform, band shaped or intestine shaped . 2 . Rosenvingea (p. 443). 



