PERONOSPORALES 1025 



somewhat bursiform, spherical, or ovoid enlargement with or with- 

 out an evacuation tube 

 Zoospores formed within a vesicle produced at the tip of an evac- 

 uation tube; antheridia never amphigynous; oospores with a 



moderately thick wall Pythium ', p. 1031 



Zoospores either extruded as an undifferentiated mass in an elongate 

 quickly evanescent vesicle or differentiated within the spo- 

 rangium; antheridia amphigynous in Phytophthora; oospore wall 

 very thick or not unusually so 

 Zoospores extruded as an undifferentiated mass in an extremely 

 long quickly evanescent vesicle; oospore wall extremely 



thi ck Pythiogeton, p. 1042 



Zoospores differentiated within the sporangium, usually emerging 

 without vesicle formation as separate motile swarmers; 

 oospore wall not unusually thick 

 Zoosporangia borne in whorls, their long axes transverse to the 



short supporting hypha Diasporangium, p. 1050 



Zoosporangia not in whorls, their long axes parallel with that of 

 the somewhat specialized sporangiophore of variable length 



Phytophthora 2 , p. 1051 



ZOOPHAGUS SOMMERSTORFF 



Osterr. botan. Zeitschr., 61 : 372. 191 1 

 (Fig. 85, p. 1029) 



Mycelium delicate, extensive, the main hyphae sparingly branched, 

 bearing numerous short peglike lateral branches modified for the 

 capturing of moving rotifers, septate or nonseptate gemmae some- 

 times formed; zoosporangium consisting of an undifferentiated 

 portion of the mycelium; zoospores produced at the tip of the dis- 

 charge tube in a vesicle or, occasionally, with vesicle lacking, lateral- 

 ly biflagellate, capable of repeated emergence; plants dioecious, 

 antheridium clavate, single, oogonium bearing a single egg. 



Parasitic on rotifers. 



Zoosporangia and sex organs have been recorded thus far only in 

 Zoophagus insidians. Sommerstorff (loc. cit.) states with respect to non- 

 sexual reproduction that in one instance he found, near the open end of 



1 See note 1 page 1024. 



2 See Waterhouse (1956). 



