PERONOSPORALl.S 1057 



"Sporangium regularly formed terminally on a long, simple or spar- 

 ingly branched, extramatrical filament measuring mostly 50 a to 2 mm. 

 in length and 2 to 2.5 \i in diameter, though often expanding in the distal 

 portion to a diameter of 3 to 5 \x; later often coming into a lateral posi- 

 tion throughcontinued elongation of the supporting filament from imme- 

 diately below the delimiting septum; regularly ovoid, but occasionally 

 bearing distally a protuberance or lobe of variable size; measuring 6 to 

 45 [.tin transverse diameter by 15 to 60 jx in length; on dehiscence open- 

 ing broadly at apex without formation of an outwardly protruding 

 papilla; after evacuation proliferous in moderate measure, both by for- 

 mation of sessile or nearly sessile secondary or often tertiary sporangia 

 within primary one and by repeated growth of the supporting filament 

 through the orifices of the empty envelope to produce additional spo- 

 rangia externally. Zoospores produced from 1 to 45 in a sporangium; 

 reniform, longitudinally grooved, biciliated, after rounding up measur- 

 ing 10 to 13 [i in diameter; individually germinating by germ-tubes 

 usually 1 to 3 in number, or often, whether properly liberated or retained 

 within the sporangial envelope owing to frustrated dehiscence, often 

 giving rise to a secondary zoospore, — the repetitional development tak- 

 ing place either by direct discharge of contents through an evacuation 

 tube 3.5 to 5.5 [jl in diameter and 1 to 10 fx in length, or by the production 

 of an elongated miniature sporangium mostly 6 to 10 jx in diameter and 

 16 to 22 [x in length on a germ sporangiophore mostly 1.5u, in diameter 

 and 10 to 60 \i in length. 



"Oogonium borne terminally on a stalk usually 5 to 15 [x in length; 

 smooth, subspherical, measuring 16 to 61 fx, mostly 42 to 52 ix (average 

 47.4 [x) in diameter; provided with a wall 0.5 to 1.7 [x (average 1.2 [i) in 

 thickness. Antheridium single; irregularly orbicular or prolate ellip- 

 soidal, sometimes provided with a distal protuberance or lobe; meas- 

 uring usually 10 to 18 [x in diameter by 14 to 20 jx in length; in some 

 (1 to 35 out of 100) cases amphigynous, but more often paragynous, in 

 latter event usually applied near base of oogonium and often in intimate 

 contact with oogonial stalk; borne laterally or terminally or in inter- 

 calary relationship on a branch mostly 5 to 50 ix in length, the branch 

 sometimes arising from a hypha not demonstrably connected with the 

 oogonial hypha, but sometimes having close mycelial connection with 



