CHAPTER VII 



PLASMODIOPHORACEAE 



THIS name was given by Zopf in 1885 to a group of organisms 

 related to Mycetozoa. The prototype genus of the group is 

 Plasmodiophora. At a later date the same group was called 

 Phytomyxineae, a supposed genus " Phytomyxa " being 

 based upon a misinterpretation of objects seen in sections 

 of root-tubercles of leguminous and other plants : " plasmic 

 masses " and rod-shaped and angular " spores " being 

 described. These were the bacteria that cause the tubercles, 

 the plasmic masses being their mucous secretion. 



The bacteria of root-tubercles benefit their hosts and 

 the land on which these grow. The Plasmodiophoraceae, 

 on the contrary, are destructive parasites. The group is 

 divided into genera according to the form and arrangement 

 of the spores, thus : -1, Plasmodiophora, with free regularly 

 shaped spores ; 2, Tetramyxa, spores in groups of four 

 enclosed in a membrane ; 3, Ligneria, variously shaped 

 spore-groups ; 4, Sorosphaera, spores grouped in a hollow 

 sphere ; and 5, Spongospora, spores forming a sponge-like 

 ball. 



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