70 



THE LOWER FUNGI— PHYCOMYCETES 



assumes a thin smooth membrane. The sporangia lie in a loose 

 cluster free from one another and only partially fill the host cell. 

 Each sporangium at maturity frees a number of biciliate swarm- 

 spores through an inconspicuous axit papilla. Other thalli 

 develop the resting stage. In W. pohjcystis Cornu occurring in 



c b. 



^S^r^-J" 



Fig. 9. — (a-g) Woronina polycystis Cornu in Saprolegnia. (h) TV. glomcrata 

 (Cornu) Fischer in Vaucheria. (a) Host hypha with two sori of swarmsporangia, 

 and at the tip a compartment in which the thallus of the parasite is as yet 

 indistinguishable from the cytoplasm of the host. {!>) Linear series of compart- 

 ments, two containing sori of swarmsporangia and two cystosori. (c) Sorus 

 of swarmsporangia. (d) Two sori of swarmporangia and three cystosori, one 

 imusually small, (e) Swarmspores delimited in sporangia. (/) Swarmspores. 

 ((7) Median section of cystosorus. {h) Sorus of resting spores, {d, and /, 

 after A. Fischer 1882; others after Cornu 1872). 



Saprolegnia the thallus fragments to form a number of resting 

 spores but these fuse forming a single large thick-walled warty 

 body termed the cystosorus (Fig. 9, a~g). In W. glomerata 

 (Cornu) Fischer, in Vaucheria, each restign spore assumes a 

 spiny wall, and a loose cluster of small spherical resting spores 

 resembling the sporangial sorus results (Fig. 9, h). 



