ORDER CHYTRIDIALES 53 



only a few species as yet, e.g., S. endohioticum by Miss Curtis (1921) and 

 S. fulgens Schroet., on Oenothera, by Kusano (1930). In the former the 

 overwintering sexually produced resting cells become deep-seated in the 

 tissues of the host by the hyperplastic division of the cells. These resting 

 cells become sporangia directly, not sori of sporangia. In S. fulgens both 

 the summer and winter generations become prosori. (Figs. 11, 12.) 



Two species of Synchytrium are of economic interest, S. vaccinii, 

 causing small galls on the leaves and fruits of the cranberry (Oxycoccus 

 macrocarpus) , and S. endohioticum, the cause of the very destructive wart 

 disease of the potato. 



Three other genera occur in this family as parasites in algae. One of 

 these is Micromyces of which the species M. zygogonii Dang, and M. longi- 



FiG. 13. Chytridiales, Family Synchytriaceae. 

 Micromyces longispinosus Couch. (A) Sorus, previously 

 extruded from the spiny prosorus, breaking up into 

 numerous zoosporangia, some of which are discharging 

 swarm cells. (B) Spiny resting spore discharging a 

 sorus, only one nucleus present. (Courtesy, Couch: 

 M?/co/o6ria, 29(5):592-596.) 



spinosus Couch have been observed in America by Couch (1937) in 

 Mougeotia and Spirogyra, respectively. The infected cells of the host are 

 usually somewhat enlarged. The plant body of the fungus is spherical 

 with numerous long spines. Through a small opening the contents emerge 

 and form a thin-walled sorus which divides into several sporangia. Within 

 these are produced numerous uniflagellate swarm spores which may infect 

 the host directly or may first unite by twos. The smaller, thick-walled 

 resting spores, which are likewise spiny, are probably the product of 

 infection by the zygotes, but this has not been proved. The resting spore 

 germinates by the extrusion of a sorus within which sporangia are pro- 

 duced. The zoospores escape when the host cell, which has usually become 

 much swollen, bursts at one side. Scherffel (1925) sets apart as the genus 

 Micromycopsis some species in which there is an exit tube from the fungus 

 body through the wall of the algal host so that the sorus, containing two 



