PLASMODIOPHORALES 789 



Sorodiscus cokeri Goldie-Smith l 



J. Elisha Mitchell Sci. Soc, 67: 108, pis. 1, 2. 1951 



(Fig. 59 CD, p. 786) 



"Obligate parasite on species of Pythium, in swellings homologous 

 with the sporangia of the host, causing little or no hypertrophy. Naked 

 Plasmodium undergoing cruciform nuclear divisions during vegetative 

 growth; at maturity partly or occasionally wholly filling the swelling, 

 and dividing into zoosporangia or resting spores. Zoosporangia thin- 

 walled, spherical to ovoid, 5.3-8.8 \x in diameter. Zoospores biflagellate, 

 with one long posterior and one short anterior flagellum; 4-11, usually 

 8 or 9, in a sporangium ; discharged through papillae formed only on 

 some sporangia on the periphery of the sorus. Resting spores 3.1-4.1 \x 

 in diameter, smooth, thick-walled, closely pressed together in circular 

 or ovoid discs one spore thick. Discs usually paired, forming curved, 

 two-layered plates; occasionally in threes or fours, giving an appearance 

 in section of Y- or H- shaped figures respectively. 



"Sporangial and resting spore membranes without cellulose, as shown 

 by a negative reaction with chlor-iodide of zinc" (Goldie-Smith, Joc.cit.). 



Parasitic on Pythium proliferum, Goldie-Smith (loc. cit.), United 

 States; from soil, substrate?, Gaertner (1954b : 22), Egypt, West Africa. 



Inoculation experiments involving such hosts as Callitriche, Nitella, 

 and species of various genera of the Saprolegniaceae and of Pythium 

 by Goldie-Smith were all negative except for Pythium irregulare, P. 

 undulatum, and P. elongatum. 



SPECIES IN AQUATIC VASCULAR PLANTS 



Sorodiscus callitrichis Lagerheim and Winge 

 Arch. f. Botanik, 12(9) :23, pi. 1, figs. 9-10; pi. 2; pi. 3, figs. 43-64. 1914 

 Parasitic in Callitriche spp. 



Sorodiscus heterantherae Wernham 



Mycologia, 27: 272, figs. 1-2, pis. 17-18. 1935 

 Parasitic in Heteranthera dubia. 



1 Emended (1956a) to include hypertrophy of host and more than four spore discs 

 in a cystosorus. 



