THE GREEN ALGAE OF NORTH AMERICA 125 



Filaments 25-32 /u. diam., cells 3-8 diam. long, fertile cells 

 slightly bent; spores globose-ovoid, 40-50 /u diam., finely punc- 

 tate, occupying the whole tube, but not projecting into the fila- 

 ments ; membrane reddish-brown. Mass., N. J. Europe. 

 The plant figured by Wolle has spores more nearly globose 

 than the usual European form. 



10. M. CRASSA (Wolle) De Toni, 1889, p. 716; Mesocarpus 

 crassus Wolle, 1887, p. 230, PI. CXLVII, fig. i. Filaments 

 about 50 fj. diam., cells 4-10 diam. long ; spores spherical, 

 smooth, about 65 /JL diam., entirely filling the tube, but not ex- 

 tending into the filaments. Florida. 



11. M. MACROSPORA (Wolle) De Toni, 1889, p. 716; Mesa- 

 carpus macrosporus Wolle, 1887, p. 230, PI. CXI/VII, fig. 4; 

 P. B.-A., No. 1368. Filaments about 30 p. diam., cells 6-10 

 diam. long; fertile cells distinctly geniculate ; spores 55-60^ 

 diam., occupying fully the tube, but not projecting into the fila- 

 ments, spherical, smooth. N. H., Pa. 



12. M. GENUFLEXA (Dillw.) Agardh, 1824, p. 83; P. B.-A., 

 No. 312 ; Mesocarpiis pleurocarpus De Bary, 1858, p. Si, PI. Ill, 

 fig. 14 ; Pleurocarpus mirabilis Wolle, 1887, p. 232, PI. CXLJX, 

 figs. 8-15. Filaments 25-33 /j. diam., cells 2-5 diam. long, 

 straight or geniculate, in the latter case often uniting with other 

 filaments, but not producing fruit in this way ; spores globose 

 or ovoid, smooth, yellowish-brown, usually formed by lateral 

 conjugation, over the dissepiment between the two conjugating 

 cells. N. Y., Mass., Me., N. J. Europe. 



A common species, forming great expansions in quiet water, 

 pale yellowish or whitish green ; \vhen removed from the water 

 the filaments soon tend to break up into the individual cells. 

 Though the species is. common almost everywhere, the fruit has 

 been considered rather rare ; but when it does occur the whole 

 mass, no matter how extensive, is usually all in fruit at once. 

 The scalariform conjugation is very rare, but has been observed 

 in this country.* 



13. M. LAETEVIRENS (A. Br.) Wittrock in Wittr. and 

 Nordst., Alg., Exsicc., No. 58 ; Craterospermum laetei'ircns*Qz. 

 Bary, 1858, p. 81, PI. Ill, figs. 1-13; Wolle, 1887, p. 235, PI. 



* Pleurocarpus columbianus Wolle, 1887, p. 232, PI. CXLIX, figs. 6 

 and 7, is described with filaments considerably larger than in M. genu- 

 flexa ; fruit is unknown; it is probably only a form of the common 

 species. The examination of a specimen from Bethlehem, Pa., marked 

 Pleurocarpus coluuibianns in Wolle's writing, shows filaments from 

 30 to 35 fj. diam. ; but little more than in M. genuflexa. 



