THE GREEN ALGAE OF NORTH AMERICA 139 



with stipitate base, and usually somewhat clavate tip ; consist- 

 ency firmer than in other species of the genus; cells 14-17 /x 

 diam., with thick and sharply marked wall, generally showing 

 little of the arrangement in fours. Minn., Montana, Alaska. 



l^n rope. 



The type is easily recognizable by its resemblance in habit 

 and texture to Enteromorpha intestinalis ; but the following 

 variety is more like other species of the genus. 



Var. extensa (Tilden) Collins, nov. comb. ; Tctraspora extensa 

 Tilden, Amer. Algae, No. 48. Fronds very long, according to 

 the author up to 35 meters, narrow, not over i cm. wide ; or 

 irregularly expanded with a diameter of 5 cm.; gelatinous, 

 bright green ; cells spherical, more or less in groups of four, 

 10-15 //. diam. I J1 sluggishly flowing water, in tanks of State 

 fish hatcheries, St. Paul, Minn. 



Much more gelatinous than the type, but apparently not dis- 

 tinct ; probably a variety due to local conditions. 



2. T. LUBRICA (Roth) Agardh, 1824, p. 188; Wolle, 1887, 

 p. 191, PL CLXV, figs. 9-n ; P. B.-A., Nos- 63, 861. Frond 

 at first attached, tubular or saccate ; soon splitting and forming 

 irregular expansions, often with many rounded openings, some- 

 times quite net-like ; up to 20 cm. long and wide, very gelatin- 

 ous, usually yellowish in color; cells 7-11 p. diam., generally 

 in fours. Fig. 26. Europe, So. America, New Zealand. 



Very common in spring, apparently everywhere throughout 

 the Northern United States ; the perforated and net-like form 

 is usually known as var. lacunosa Chauvin, but really has no 

 characters by which it can be distinguished from the type. 



3. T. GELATINOSA (Vauch.) Desvaux, 1818, p. 18 ; Wolle, 

 1887, p. 191 ; P.hyk. Univ., No. 693 ; Ulva gelatinosa Vaucher, 

 1803, p. 244, PI. XVII, fig. 2. Forming inflated bullate masses, 

 not lacunose ; very soft and gelatinous; cells 2.5-13 p. diam., 

 very different sizes being found side by side in the same frond. 

 Me., Mass., N. J., Iowa, Cal. Europe. 



Generally distributed in quiet water ; the fronds are more 

 rounded than in other species, and the lack of uniformity in the 

 size of the cells is marked. But there are intermediate forms 

 between it and T. lubrica* 



*T. bullosa, rioted iu practically all manuals of fresh water algae, is now 

 pretty well known to be a Monostroma ; it seems to be not uncommon 

 in Europe, but no American specimens have been seen. The American 

 specimens passing under the name of T. bullosa var. cylindracea (Hilse) 



