THE FUNGI WHICH CAUSE PLANT DISEASE 83 



periplasm bearing the degenerate supernumerary nuclei. Fer- 

 tilization is as in the Albugos that have an uninucleate 



ggg_41, 44, 52, 53 



The family has suffered many revisions of classification and 

 much renaming of genera. Plasmopara and Peronospora are 

 especially rich in a masquerade of names.^''* ^*'''''' 



Key to Genera of Peronosporaceae 



Conidiophores scorpioid-cymosely branched ; 



conidia germinating by zoospores 1. Phytophthora, p. 84. 



Conidiophores simple, monopodially or 



dichotomously branched. 



Conidiophores simple or monopodially 



branched; conidia germinating by 



zoospores or by a plasma 



Conidiophores simple or irregularly 



branched 2. Kawakamia, p. 89. 



Conidiophores regularly branched 

 Conidiophores with the main axis 

 indurate, the lateral branches 



reduced and basidiarlike 3. Basidiophora, p. 89. 



Conidiophores with the main 

 axis not indurate, the lateral 

 branches developed normally. 

 Conidiophores fugacious, stout, 

 sparingly branched; oospore 

 permanently united to the 



wall of the oogonium 4. Sclerospora, p. 89. 



Conidiophores persistent, slender, 

 usually freely branched; oo- 

 spore free from the wall of 

 the oogonium 

 Branches of the conidiophore 



apically obtuse 5. Plasmopara, p. 90. 



Branches of the conidiophore 



apically acute 6. Peronoplasmopara,p.93. 



Conidiophores dichotomously branched; 

 conidia germinating by a germ tube. 

 Conidiophores with subapical disk-like 

 enlargements from which the ul- 



