20 TUFTS COLLBGB STUDIES, VOL. IV, No. 7 



3. Conjugation geniculate. 13. M. laeleritens. 



3. Conjugation not genicnlate. 4. 



4. Filaments usually genicnlate ; conjugation almost always lateral. 



12. M. genuftexa, 



4. Filaments not genicnlate ; conjugation scalariform. 5. 



5. Spore smooth. 6. 



5. Spore pitted or punctate. 13. 



6. Filaments 20 M diam. or more. 7. 



6. Filaments 15 M diam. or less. 9. 



7. Spore projecting into the cell on each side. 8. 



7. Spore occupying the tube only. n. 



8. Spore about 60 M diam. 5. M. ininn f sot f nit's. 



8. Spore 45 M diam. or less. 10. 



9. Filaments 12-14 M diam. 7. M. delicatula. 



9. Filaments 6- IOM diam. 3. M.parvula. 



10. Fertile filaments straight. 4. M. sphaerocarpa. 



10. Fertile filaments undulate. 6. M. divaricate. 



II. Filaments about 50 M diam. 10. M. crassa. 



li. Filaments 30 M diam. or less. 12. 



12. Spore 55-60 M diam. u. M. macros flora. 



12. Spore 30-40 ft diam. i. M. sea/art's. 



13. Spore transversely ovoid. 8. M.verrucosa. 



13. Spore globose or nearly so. 14. 



14. Filaments 8-10, rarely 15 M diam. 2. M. nummuloides. 



14. Filaments 22-32 M diani. 9. M. robusla. 



15. Spore normally bounded by 3 cells. 14. M. tenttis. 



15. Spore normally bounded by 4 cells. 16. 



16. Spore punctate or scrobiculate. 17. 



16. Spore smooth. 18. 



17. Filaments 8-12 M diam. 15. M. quadrangnlata. 



17. Filaments 6-8.5 M diam. 2 5- 



18. Filaments bluish or purplish with age. 18. flf. cap*ci*a. 



18. Filaments not becoming bluish or purplish. 19. 



19. Filaments 10-12 M diam. 20. 



19. Filaments 8 M diam. or less. n. 



20. Spore globose to angular globose, wall of uniform thickness. 



19. M. calcarea. 



20. Spore transversely ellipsoid, wall thicker at poles. 



24. M. bicalyptrata. 



21. Spore quadrangular with concave aides. 16. A/, viridts, 



21. Spore quadrangular with straight sides. 17. M. (legantula. 



22. A planonpores spherical. 19. M. calcarea. 



22. Aplanospores elongate or snbpolygonal. 23. 



23. Aplanospore* swollen on one side only. 20. M. rtniricoia. 



23. Aplanospores swollen on both sides. 24 



