1044 AQUATIC PHYCOMYCETES 



and of the sizes of the parts as characters of diagnostic importance— the 

 primary bases on which all but two species of the genus are now sepa- 

 rated — awaits the results of extensive studies of fungi identifiable with 

 Minden's species as well as of those described since his time. 



KEY TO THE SPECIES OF PYTHIOGETON 



Sporangia bursiform or irregularly saccate 

 Sporangia for the most part terminal 



Sporangia predominantly broadly bursiform, the discharge tube 

 nearly parallel with the axis of the attendant hypha ; spo- 

 rangiferous hyphae sparingly branched ; oogonia spherical 



P. ut ri forme, p. 1044 

 Sporangia predominantly narrowly bursiform, the discharge tube 

 approximately at right angles to the axis of the attendant 

 hypha; sporangiferous hyphae richly branched; sex organs 



unknown P. ramosum, p. 1046 



Sporangia for the most part intercalary 



Sporangia (four) averaging 154 \l long by 60.5 \i in diameter; 



oogonia polygonal P. transversum, p. 1047 



Sporangia (one hundred) averaging 96 \i long by 42 u. in greatest 



diameter; sex organs unknown P. autossytum, p. 1048 



Sporangia spherical or ovoid 



Sporangia 40-56 by 30-40 [a; discharge tube 39-70 \x long 



P. uniforme, p. 1049 

 Sporangia 20-34 by 18-28 [x; discharge tube 4.8-15 \l long 



P. dichotomitm, p. 1049 



PYTHIOGETON UTRIFORME Millden 



Falck, Mykolog. Untersuch. Berichte, 2(2): 242, pi. 6. figs. 56-65. 1916 



(Fig. 88 F-N, p. 1045) 



Mycelium composed of slender sparingly branched hyphae 2.5-3.5 [x 

 in diameter; zoosporangium terminal, bursiform or somewhat irregular, 

 the discharge tube slender, more or less prolonged, its long axis frequent- 

 ly nearly parallel with that of the supporting hypha; zoospores reniform, 

 laterally biflagellate; oogonium predominantly spherical, averaging 45 u. 

 in diameter, antheridium single, monoclinous, hemispherical, sometimes 

 bearing a short appendage, applied laterally or near the base of the 

 oogonium, forming a fertilization tube; oospore spherical, completely 



