35. Sporangia inflated only on outer side; vegetative 



cells S0S5/M in diameter S. Borgeana 



35. Sporangia inflated mostly on the inner ( conjugating ) side 36 



36. Vegetative cells 23-30,li in diameter ..S. Teodoresci 



36. Vegetative cells 30-40/x in diameter S. varians 



37. Spores 28SS/J. in diameter, short, up to 50ju long; 



sporangia decidedly inflated „ S. affinis 



37. Spores averaging smaller, 24-30^ in diameter, and much longer 



up to 90m; sporangia slightly inflated to 38/a- - S. catenaeformis 



38. Conjugation by geniculate bending of filaments, without 



conjugation tubes (Sirogoniiim of some authors) 39 



38. Conjugation by tubes formed from both cells 40 



39. Vegetative cells 38-56,ti in diameter; spores 41-64nt 



in diameter; median spore wall smooth . S. stictica 



39. Vegetative cells 51-60ai in diameter; spores 63-70|U in diameter; 



median spore wall wrinkled or granular S. pseudofloridana 



40. Median spore wall smooth 41 



40. Median spore wall not smooth 49 



41. Vegetative cells 125-150m in diameter S. ellipsospora 



41. Vegetative cells smaller 42 



42. Conjugating cells inflated (or cylindric in S. majuscula) 43 



42. Conjugating cells cylindric — . .-.- ..44 



43. Vegetative cells 50-80/^ in diameter; chloroplasts 3-8 S. majuscula 



43. Vegetative cells 40-50/i in diameter; chloroplasts 2-3 S. dubia 



44. Vegetative cells more than 45/Lt in diameter .45 



44. Vegetative cells less than 45^ in diameter 46 



45. Spores 60-80-(85)/u in diameter, 90-170m long, ends pointed S. r.itida 



45. Spores 87-108^ in diameter, 120-155^ long, ends not pointed S. jugalis 



46. Spores ovate, cylindric-ovate ( sometimes nearly globose ) 47 



46. Spores ellipsoid ....48 



47. Chloroplasts 3; spores ovate to subglobose, 



34-48m in diameter, 48-54^ long S. triplicata 



47. Chloroplasts 2 (rarely 3 in some cells of the filament); spores 

 cylindric-ovate to subglobose, 31-40/x in diameter, 31-68/i long . S. decimina 



48. Vegetative cells 40-44^ in diameter, up to 240/^ long; chloroplasts 



3, making 1-2 turns; spores 32-40^ in diameter S. Fuellebornei 



48. Vegetative cells averaging smaller, 36-41/a in diameter, up to 



400m long; chloroplasts 2-.3, making 2^2 to 3^2 turns S. rivularis 



49. Vegetative cells more than 100/x in diameter 50 



49. Vegetative cells less than 100^ in diameter 51 



50. Vegetative cells 140-165^ in diameter; spores 



compressed-ovate; median spore wall pitted S. crassa 



50. Vegetative cells 118-140-( 153)m in diameter; spores 

 compressed-spheroid; median spore wall reticulate S. maxima 



51. Spores ellipsoid - 52 



51. Spores ovate -- 53 



52. Zygospores 32^2|U in diameter, wall finely scrobiculate S. oriertalis 



52. Zygospores averaging larger, 38-62^ in diameter; median spore 



wall irregularly reticulate S. rhizobrachialis 



53. Vegetative cells 23-25-(29)/u in diameter S. aequinoctialis 



53. Vegetative cells larger 54 



54. Fertile cells cylindric — S. novae-angliae 



54. Fertile cells inflated — S. fluviatilis 



[310] 



