Brand: stapfia cylindrica in Minnesota. 7.3 



tion by which buoyancy is secured and the ordinary upright 

 position of the thallus is made possible. The structure may be 

 produced by the degeneration of the gelatin of the interior. 



The plant very strongly resembles Entcromorpha intestinalis 

 of marine waters in its pale green color, subtubular thallus, 

 variability in size and attenuate base. 



The plants of Nordstedt, Wittrock and Lagerheim, no. 1362, 

 distributed as Tetraspora cylindrica (Wahlenb.) Ag. f. entero- 

 morphoides Lagerh. nov. form, which, according to Chodat, no 

 doubt belongs to the genus Stapfia, resembles the Lake Superior 

 form considerably, though there are some dissimilarities as may 

 be seen by a comparison of the two. The thallus of the former 

 is fistulose, while that of the Lake Superior plant is subfistulose 

 or alveolar. They agree in that both are verrucose, but dis- 

 agree in that the former may sometimes be ramose, the latter 

 never. The former is described by Lagerheim as "fragili," 

 while the latter is firm and quite tough. They differ also in 

 color, the former being of a much darker green. The Lake 

 Superior form, however, is darker in color in quiet, less fresh, 

 water. The former has rather short thalli in comparison to the 

 diameter, while the Lake Superior plant has a thallus long and 

 of relatively small diameter. The former is much like the 

 larger of the type specimens distributed by Stapf as Stapfia 

 cylindrica, while the latter resemble very much the slender 

 and relatively much longer specimens of the same distribution. 

 There is also the great difference in habitat, the one being 

 found in the largest of the fresh-water lakes and the other in a 

 swift-flowing alpine stream of northern Norway. 



Exteriorly the plant resembles most strongly the specimens 

 distributed by Rabenhorst as no. 2244, Tetraspora cylindrica. 

 There is, however, a greater variance in length. The shortest 

 of my specimens are about as long as the longest of Rabenhorst, 

 while the longest are nearly as long as Wittrock and Nordstedt's 

 Tetraspora cylindrica forma rivularis. The former were col- 

 lected on rocks in Lake Wettern, near Jonkoping, Sweden, by 

 Nordstedt, and the latter were also collected by him near Kongs- 

 vold, Norway, in the river Driva. 



The Lake Superior form may be described as follows : 



Thallus 2-5 mm. in diameter, 6 cm. to 3 dec. in length, 

 dilute green in color, erect, gelatinous, cylindrical, subfistulose, 

 sometimes rugose-verrucose, unbranched, firm, rather tough, 



