PLATE CXII1. 



4 



FIGS. PAGE 



1-7. Xanthidium variabile (Nordst.) W. & Gr. S. 

 West. 1 and 2, x 570 (after Nordstedt) ; 

 3-6, x 520; 7, zygospore, x 520. . 81 



8. X. Robinsonictnum Arch. x 520 . 83 



9. X. apiculiftriim West, x 625 . . 85 



10-12. X. Orcadense W. & G. S. West. x 520 84 



13-15. Arthrodesmus Incus (Breb.) Hass. x 520 . 90 

 16-19. A. Incus forma minor. 16, x 400 ; 17, x 520; 



18, x 400; 19, zygospore, x 520 . . 92 



20-23. A. Iiicus var. iudentatus W. & G. S. West. 20, 



x 520; 21 and 22, x 500; 23, x 520 94 



24. A. Incus var. indentatus forma scrobiculata. x 



520 94 



