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



i. MOUGEOTIA Agardh, 1824, p. XXVI. 

 Cells cylindrical, several times as long as broad ; dissepi- 

 ments somewhat lens-shaped ; chromatophore an axillary plate 

 with two or more pyrenoids; zygospores formed in the tube, 

 sometimes occupying the whole width of one or both of the orig- 

 inal cells, thus bounded by 2, 3, or 4 cells ; spore with two 

 membranes, the outer colored, smooth or sculptured ; akinetes, 

 when occurring, with single membrane, formed by a division of 

 the mother cell into three parts, of which the middle part be- 

 comes the akinete. 



KEY TO THE SPECIES OF MOUGEOTIA. 



i. Fertile cell bounded by 2 cells. Sect. MESOCARPICAE 2. 



i. Fertile cell bounded by 3 cells. Sect. PI,AGIOSPERMICAE. 



14. M. tennis. 



i. Fertile Cell bounded normally by 4 cells, exceptionally by 2 or 3. 

 Sect. STAUROSPERMICAE. 13. 



2. Conjugation scalariform. 3. 



2. Conjugation lateral, rarely scalariform. 12. M. genuflexa. 



2. Conjugation geniculate. 13. M. laetevircns. 



3. Spore smooth. 4. 



3. Spore pitted or punctate. n. 



4. Filaments 15 M diam. or less. 3. M. parvula. 



4. Filaments 20 M diam. or more. 5. 



5. Spore diam. greater than length of tube; spore extending into the 



cell on each side. 6. 



5. Spore occupying the tube only. 9. 



6. Spore 60 /j. diam. 5. M. minnesotensis. 



6. Spore 45 /j. diam. or less. y. 



7. Filaments 15 ^ diam. or less. 7. M. delicatula. 



7. Filaments 20 fj. diam. or more. 8. 



8. Filaments straight. 4. M. sphaerocarpa. 



8. Filaments geniculate. 6. M. divaricata. 



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



9. Filaments 30 M diam. or less. 10. 



10. Spores 55-60 M diam. u. M. macrospora. 



10. Spores 30-40 /JL diam. i. M, scalaris. 



n. Spores transversely ovoid, extending into the filaments. 



8. M. verrucosa. 

 ii. Spores globose or nearly globose. 12. 



12. Filaments 8-10 /JL, rarely 15 M diam. 2. M, nummnloides. 



12. Filaments 25-32 /* diam. 9. M. robusta. 



13. Spores punctate. 15. M. quadrangulata. 



13. Spores smooth. !4. 



14. Filaments bluish or purplish with age. 18. M. capucina. 



14. Filaments not bluish or purplish with age. 15. 



