120 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



appearance; zygospore formed in the tube, with smooth, sac- 

 cate, yellowish, translucent outer membrane, and browish-yellow 

 median membrane, with three longitudinal parallel ridges, con- 

 nected by fine, radial cross lines. 



D. GLYPTOSPERMA (De Bary) Wittrock, 1872, p. 35; P. 

 B.-A., No. 1419. Mougeotia glyptosperma De Bary, 1858, p. 78, 

 PI. VIII, figs. 20-25; Wolle, 1887, p. 229, PI. CXLVI, figs. 

 6-9. Filaments crisped, lubricous, 10-15 f- diam.; cells 6-12 

 diam. long ; fertile cells still longer ; spores ovoid, 42-49 X 30-40 

 p.. Fig. 9. Mass., Minn., Florida. Europe, New Zealand. 



The peculiarly striate spores, ovoid, set lengthwise of the 

 tube, occupying the whole space between the filaments, dis- 

 tinctly characterize this species. 



4. ZYGOGONIUM Kiitzing, 1843, p. 280. 



Cells cylindrical, as long as broad to twice as long ; dissepi- 

 ments even ; two axillary, irregular chromatophores, each with 

 one pyrenoid ; zygospore formed in the tube between two cells 

 not differing in appearance ; the prolongation from each cell 

 cut off from the rest of the cell by a wall, before uniting with 

 the prolongation from the other cell ; akinetes sometimes 

 formed, as in Zygnema. 



The protoplasm that is to take part in the formation of the 

 zygospore gathers at the newly formed tube, and is cut off from 

 the mother cell ; then the wall at the end of the tube is dissolved 

 where it touches the tube from the other cell, and the two 

 recently formed small cells unite to form the spore. In Zygnema 

 the spore is formed in a tube which still communicates with 

 both the filament cells. This is practically the only difference 

 between the genera, though the chromatophore is less regularly 

 star-shaped in Zygogonium than in Zygnema. 



Z. ERICETORUM Kiitzing, 1845, p. 224; Z. Agardhii Wolle, 

 1887, p. 226, PI. CXLV, figs. 6 and 7. Filaments 15-25 p. 

 diam., cells 1-4 diam. long, greenish, becoming brownish, pur- 

 plish, or blackish by exposure to air and sun ; spores globose to 

 ovoid, 20-25 P- diam. Fig. 10. 



Var. TERRESTRE Wittr. and Nordst., Alg. Exsicc., No. 

 1594 ; P. B.-A., No. 519. Color more uniformly purple or 

 violet ; cells somewhat constricted at the nodes ; often with 

 short rhizoidal branches ; wall thicker and stouter ; seldom 

 fruiting. On moist ground. Both type and variety, Maine, 

 Mass., Florida. Europe, So. America. 



