THE GREEN ALGAE OF NORTH AMERICA 407 



In appearance not unlike a Vaucheria, but of more erect habit, 

 and lacking the elaborate sexual apparatus of that genus. 



2. D. MARINA (L,yng.) Kjellman, 1883, p. 316 ; D. temus- 

 sima P. B.-A., No. 574.* Arising from a more or less distinctly 

 developed layer of irregular creeping cells ; erect filaments 

 bright green, 50-70 /A diam., sometimes simple but usually with 

 a few lateral branches similar to the axis ; a cell partitioned off 

 frequently near the base of a branch, and occasionally in the 

 axis just above a branch, not much smaller than the branch, 

 about as long as broad ; sporangium occupying the place of a 

 branch, 150-250X90-200 /A, from obovoid to subspherical ; pedi- 

 cel varying from 30-70 /u. in length, 30-35 /u, diam., the cell formed 

 in it being about as long as broad ; spores 20 or more in a spor- 

 angium. Fig. 152. Alaska to Southern Cal. Europe. 



3. D. LAMOUROUXII (J. Ag.) Solier, 1847, p. 162, PI. IX, 

 figs. 18-30; Biyopsis simplex Rabenhorst, Algen, No. 916. 

 Filaments arising from a creeping base, from a few cm. to 2 

 dm. high, 100-600 /u. diam., dark green, rather stiff, sometimes 

 simple, sometimes with more or less numerous irregular 

 branches; sporangia globose, 300-550 ^ diam., sessile or on a 

 short and slender pedicel. Southern Cal. Europe. 



Distinguished from our other species by the much larger fila- 

 ments. Only sterile plants have yet been found here, and 

 though they agree very well with the Mediterranean plant, the 

 identification is uncertain until fruit is observed. 



Family 4. PHYLLOSIPHONACEAE. 



Frond filiform, inarticulate, branching; perforating the shells 

 of mollusks, or parasitic in the tissues of plants ; asexual repro- 

 duction, known only in one genus, by aplanospores. 



The family was founded on the genus Phyllosiphon ; the in- 

 clusion of Ostreobiiun, so totally different in its habitat, may seem 

 hardty warranted ; but the two resemble each other in the form 

 of the vegetative frond more than they do any other genus ; the 

 reproduction of Ostreobium being quite unknown, the present 

 place is as suitable as any for it, temporarily. 



KEY TO THE GENERA OF PHYLLOSIPHONACEAE. 



i. Parasitic in the tissues of plants. i. PHYLLOSIPHON. 



i. Perforating the shells of mollusks. 2. OSTREOBIUM. 



* D. tenmssiina (De Not.) Crouan, of southern Europe, has sporangia 

 sessile, without the short cell. 



