THE GREEN ALGAE OP NORTH AMERICA 127 



late; spore 20-24 /x long and wide, 12-14/0. thick, in face view 

 cruciform-quadrate, in side view subelliptic with truncate 

 apices ; outer membrane smooth, hyaline, in front view with 

 slightly rounded angles, in side view oval. W. I. Sweden. 



18. M. CAPUCINA (Bory) Agardh, 1824, p. 84; P. B.-A., 

 Nos. 563, 1420 ; Staurospermum capucinum De Bary, 1858, p. 81 ; 

 Wolle, 1887, p. 234, PI. CL, figs. 1-5. Filaments 15-20 /x diam., 

 cells 6-14 diam. long, fertile cells sometimes shortened ; spores 

 dark red to ochre color, cruciate to quadrangular with much 

 concaved sides ; seen from the edge, linear oblong ; occupying 

 the width of both filaments ; membrane smooth. Mass., N. J. 



Europe. 



Forming masses which except when quite young have a color 

 ranging from bluish to deep violet. 



19. M. CALCAREA (Cleve) Wittrock, 1872, p. 40, PI. II. 

 Filaments 10-14 P- diam., cells 4-20 diam. long ; slightly genic- 

 ulate in conjugation ; spores van-ing in form, mostly glo- 

 bose or angular-globose, 21-50, usually 30 //, diam.; membrane 

 brown, smooth. 'Greenland. Europe. 



It was in this species that the different modes of spore forma- 

 tion, supposed to distinguish different genera, were first ob- 

 served occurring on one individual. 



2. GONATONEMA Wittrock, 1878, p. 9. 



Vegetative cells as in Mougeotia; conjugation unknown; 

 aplanospore with double membrane formed in the middle of an 

 elongated cell, the portions each side of the spore being shut off 

 by the formation of cross walls. 



G. VENTRICOSUM Wittrock, 1878, p. 16, figs. 1-13; Wolle, 

 1887, p. 233, PI. CXIvIX, figs. 1-5; Wittf. and Nordst., Alg. 

 Exsicc., No. 652; G. notabile, P. B.-A., No. 1174. Filaments 

 5-7 p. diam., somewhat bent geniculately, cells 6-16 diam. long ; 

 spores obliquely elliptic, one side being more convex than the 

 other; seen from the side, elliptic, 22-29 X 13-16 /A ; 12-15 p. 

 thick, yellowish, smooth. Fig. n. Pa., Cal. Europe. 



Order VOLVOCALES. 



Vegetative cells always motile, or readily passing into a motile 

 stage as vegetative cells, solitary or united into disk, spherical, 

 or other shape, but not into filaments. Cells uninucleate ; 

 chromatophore usually cup-shaped. 



KEY TO THE FAMILIES OF VOLVOCALES. 

 i. Cells free, never forming colonies. i. CHLAMYDOMONADACEAE. 



