358 AQUATIC PHYCOMYCETES 



PHYSORHIZOPHIDIUM Scherffel 



Arch. Protistenk., 54: 181. 1926 

 (Fig. 19 G, p. 318) 



Thallus epi- and endobiotic, monocentric; sporangium inoperculate, 

 formed near the surface of the substratum from the enlarged body of 

 the encysted zoospore and producing by the deliquescence of a papilla 

 one or more pores for the escape of the zoospores; thallus with an 

 endobiotic swelling with or without rhizoids and a secondarily formed 

 epibiotic subsporangial swelling; zoospores posteriorly uniflagellate, 

 produced within the sporangium, with a single oil droplet; resting spore 

 not observed. 



On diatoms. 



Distinct from Phlyctidium and Rhizophydium primarily in the second- 

 ary formation of a subsporangial epibiotic knoblike swelling. 



PHYSORHIZOPHIDIUM PACHYDERMUM Scherffel 



Arch. Protistenk., 54: 181, pi. 9, figs. 21-40. 1926 



Sporangium at first spherical, by the formation of a broad conical 

 truncate outgrowth from one side becoming at maturity ovate, humped, 

 or irregular, 8-21.6 \x high by 10-27 \x long, generally with the long 

 axis at right angles to that of the penetration tube, with a thick smooth 

 wall on which is formed at or near the tip of the conical lateral outgrowth 

 a single prominent conical basally, laterally, or apically directed thin- 

 walled discharge papilla; haustorium typically spherical, provided with 

 delicate branched rhizoids (?) and, between the outer surface of host 

 wall and the base of sporangium, with an epibiotic, subsporangial 

 swelling of the same size as, or slightly larger than, the haustorium; 

 zoospores spherical, 2.7 \x in diameter, with a single minute (less than 

 1 \l) eccentric basal oil droplet and a posterior flagellum from four to 

 five times as long as the body, emerging actively through a pore 3-7 \x 

 in diameter formed upon the deliquescence of the papilla; resting spore 

 not observed. 



Parasitic on Amphora ovalis, Scherffel (loc. cit.), Hungary; Navicula 

 sp., Sparrow (1943: 242), United Statfs. 



