THE GREEN ALGAE OF NORTH AMERICA 123 



15. Filaments 10-12 n diam. 19. M. calcarea. 



15. Filaments 8 /x or less. 16. 



16. Spores quadrangular with concave sides. 16. M. viridis. 



16. Spores quadrangular with straight sides. 17. M. elegantula. 



1. M. SCALARIS Hassall, 1842, p. 45; P. B.-A., No. 963 ; 

 Mesocarpus scalaris Wolle, 1887, p. 230, PL CXI/VII, figs. 2 

 and 3 ; Sphacrocarpus scalaris Kiitzing, 18553, p. 2, PI. V, fig. i. 

 Filaments 25-30 /tx diam., rarely 20-23 / x cells 2-6 diam. long, 

 rarely more ; fertile cells somewhat elongate, slightly genicu- 

 late ; spores 30-38 /x diam., globose or slightly ovoid, membrane 

 yellowish brown, smooth, occupying the tube between the two 

 straight or very slightly bent cells.* Mass., N. J. Europe. 



2. M. NUMMULOIDES (Hass.) De Toni, 1889, p. 713; 

 P. B.-A., No. 714; Mesocarpus nummuloides De Bary, 1858, p. 

 80, PI. VIII, figs. 9 and 10; Wolle, 1887, p. 231, PI. CXLVIII, 

 figs, i and 2. Filaments 8-10 /x, rarely 15 /x diam., cells 5-12 diam. 

 long; spores globose or broadly ovoid, 17-23 /x diam., rarely 

 larger, occupying the tube but not extending into the filaments ; 

 membrane brown, pitted. Me., Mass., N. J. Europe. 



3. M. PARVULA Hassall, i843b, p. 434; Mesocarpus parvulus 

 DeBary, 1858, p. 80, PI. II, fig. 15; Wolle, 1887, p. 230, PI. 

 CXLVIII, figs. 3 & 4. Filaments 6-10 /x diam., cells 5- 1 2 diam. 

 long; spores globose, 8-24 /x diam., occupying the tube and 

 sometimes projecting very slightly into the filaments ; membrane 

 brown, smooth. f " Pools, north, south and west." Wolle. 



Europe. 



4. M. SPHAEROCARPA Wolle, 1887, p. 227, PI. CXLVI, 



figs, i and 2; P. B.-A., No. 1173. Filaments 20-25 /x diam., 

 cells 3-6 diam. long; spores spherical, about 40 /x diam., 



* M. recurva (Hass.) De Toni, 1889, p. 714; Mesocarpus recurvus Wolle, 

 1887, p. 231, PL CXLVII, fig. 6, if the plate is correctly drawn, would 

 seem to be a smaller M. scalaris, or a larger M. parvula Hass., and 

 hardly an autonomous species. 



M. radicans Wolle, 1887, p. 231, PI. CXL/VIII, figs. 7-10, can hardly be 

 M. radicans Kiitz., 18553, p. i, PI. Ill, fig. I, which has rhizoidal 

 branches smaller than the filaments, while Wolle's figures show branches 

 as large as the filaments and of the same appearance. An examination 

 of au authentic specimen shows the figures to be correct, although the 

 branching is not as abundant as represented. Possibly, as suggested by 

 Wolle, it is an abnormal condition of M. scalaris. 



t M. parvula var. angusta (Hass.) Kirchner. Under this name is dis- 

 tributed in Tilden, Amer. Algae, No. 284, a sterile plant, grown in an 

 aquarium under abnormal conditions ; it can hardly be considered a cer- 

 tain determination. 



