35. Oogonia broadly pyriform, 40-45m long, smooth Oe. megaporum 



36. Vegetative cells capitellate — . -. - -- -- . -- 37 



36. Vegetative cells cylindric (cf., however, Oe decipiens var. dissimile) -39 



37. Oospores (29)S0S2n in diameter Oe. pseudoplenum 



37. Oospores smaller 38 



38. Oogonia pyriform-globose, 34— 39ai in diameter; oospores not nearly 

 filling the oogonia; plants always gynandrosporous Oe. Areschougii 



38. Oogonia depressed-globose, 29S8/J. in diameter, reproductive struc- 

 tures averaging smaller throughout; oospores nearly filling the oogo- 

 nia transversely; idioandrosporous or gynandrosporous Oe. suhplenum 



39. Oogonia 30-38/x in diameter; vegetative cells 



9-12/i in diameter — Oe. decipiens 



39. Oogonia 39-46/x in diameter; vegetative cells averaging 



larger, 10— 16/ot in diameter Oe. tnacrospermum 



40. Oogonia terminal, with longitudinal 



ridges on inner surface „ Oe. acrosporum 



40. Oogonia terminal or intercalary, without longitudinal ridges 41 



41. Oospore wall smooth 42 



41. Oospore wall layers (either middle or outer) decorated 



with pits, scrobiculations, or striations 47 



42. Vegetative cells 4-8/a in diameter 43 



42. Vegetative cells larger.. — 44 



43. Oogonia obovoid; oospores 19-25^ long .. . . Oe. ruguloswn 



43. Oogonia ovoid to ellipsoid; oospores shorter, 17-20^ long ... Oe. longatum 



44. Opening of oogonia supreme — — - ..-.Oe. michiganense 



44. Opening of oogonia superior 45 



45. Oogonia 43-50^ in diameter Oe. ciliatum 



45. Oogonia smaller, 31-42/u in diameter - 46 



46. Oospores completely filling the oogonia 



tra aversely; gynandrosporous Oe. hians 



46. Oospores not completely filling the oogonia 



idioandrosporous ( as far as known ) -— Oe. macrandrium 



47. Vegetative cells 4.5-6m in diameter —Oe. polyandrium 



47. Vegetative cells larger - 48 



48. Median layer of oospore with 16-30 anastomosing ridges; 



vegetative cells 20-30^ in diameter Oe. Croasdaleae 



48. Median layer of oospore wall scrobiculate; vegetative cells smaller 49 



49. Suffultory cell enlarged, 21-29^ in diameter _____ __ Oe. monilc 



49. Suffultory cell not enlarged - - Oe. Ackleyae 



50. Oogonia opening by a pore (poriferous) 51 



50. Oogonia opening by a hd (operculate) ___ 118 



51. Monecious (when specimens under observation are incomplete, 

 several plants should be studied; incomplete specimens may be 



sought under the dioecious section of the poriferous species) 52 



51. Dioecious -_ - '" 



52. Vegetative cells 1.8-2^ in diameter ._ Oe. angustissimum 



52. Vegetative cells larger 53 



53. Pore median 54 



53. Pore supramedian or superior _ 58 



54. Median wall of oospore areolate Oe. areolijerum 



54. Median wall of oospore smooth - 55 



55. Oogonia 42-50^ in diameter Oe. fragile 



55. Oogonia smaller 56 



r 159] 



