SYNCHYTRIACEAE 



a 



escape to the exterior through an exit tube. According to Ku- 

 sano (1912), motile biflagellate zygotes arise in O. viciae by 

 fusion in pairs of zoospores (gametes). The zygotes soon come 

 to rest and produce a wall, and their contents escape into the 

 host to become thick-walled, resting sporangia. Presumably the 

 first divisions of the zygote nuclei are reductional. 



Fig. 17. Olpidium brassicae from roots of cabbage seedlings. A. Sporangia. 

 B. Zoospores. C and D. Mature resting spores. {A and B after Woronin, 



C and D after Bensaude.) 



SYNCHYTRIACEAE. Approximately 75 species comprise the 

 Synchytriaceae. Nearly all are parasitic on seed plants, causing 

 excrescences. Two species, Synchytrhnn vaccmiiy on the leaves 

 and fruits of cranberry, and S. endobioticiim, on potato tubers, 

 are of especial interest. The latter causes excrescences to form, 

 whence the name potato wart. These excrescences vary from 

 small growths the size of a pea to enlargements exceeding the 

 size of the tuber from which they arise. The disease was first 

 discovered in upper Hungary and is now known to occur 

 throughout Europe and Great Britain; it appeared in the United 

 States in 1918. The causal organism was given the name 

 Chrysophlyctis endobiotica by Schilberszky (1896). 



