LAGENIDIALES 961 



Petersenia irregulare (Constantineanu) Sparrow 



Aquatic Phycomycetes, p. 634. 1943 



(Fig. 75 H, p. 939) 



Olpidiopsis irregularis Constantineanu, Revue Gen. Bot., 13: 373, figs. 76 

 A-K, 77. 1901. 



Sporangium predominantly irregularly tubular, with short contorted 

 branches or lobes of varying length, occasionally ellipsoidal or narrowly 

 reniform, the whole complex 40-90 u, long, causing pronounced 

 swelling of the infected part (generally the apex) of the hypha, with a 

 single short sessile or slightly protruding discharge tube; zoospores 

 somewhat reniform, 4.5-5 \x long by 3-4.5 \x wide, with a few granu- 

 lations or a small droplet and two unequal oppositely directed flagella, 

 the anterior one shorter than the posterior, emerging quickly in a group 

 or individually through the orifice of the discharge tube, movement 

 slow and even; resting spore not observed. 



Parasitic in hyphae of Saprolegnia sp., Constantineanu (loc. cit.), 

 Rumania; Achlya sp., Sparrow (1934c: 15), Denmark; Achlya sp. 

 (Michigan) United States. 



Minden (1915:264) considered the species a doubtful member of 

 Olpidiopsis, since no resting stage was observed. Observations on this 

 phase of the present species as well as on Petersenia lobata and P. 

 pollagaster may result in its segregation from Petersenia as well. 



IMPERFECTLY KNOWN SPECIES OF PETERSENIA 



? Petersenia sp. Aleem 

 Vie et Milieu (Bull. Lab. Arago), 1 : 429, figs. 13-16. 1950 

 Parasitic on Acrochaetium eodii, France. 



PSEUDOSPHAERITA Dangeard 



Le Botaniste, 4: 242. 1894-95 



(Fig. 76 A, p. 960) 



Thallus endobiotic, holocarpic, contents vacuolate during maturity: 

 sporangium without a discharge tube; zoospores biflagellate.the flagel- 

 la attached subapically, the shorter directed anteriorly, the longer 



