780 AQUATIC PHYCOMYCETES 



borne like the sporangia sorus, cysts spherical or ellipsoidal, 12-22 \i in 

 diameter, thick-walled, the outer wall reticulate with minute spines, 

 upon germination forming a flasklike tube which pierces the algal wall 

 and through which the zoospores presumably escape. 



Parasitic in Vaucheria terrestris, V. sessilis, Cornu (loc. cit.), France ; 

 Vaucheria terrestris, V. sessilis, Zopf (1894: 43, pi. 2, pi. 3, figs. 1-3), 

 Minden (1915:275), Germany; Vaucheria sessilis, Voronichin (1920: 

 10), Russia; Vaucheria sp., Valkanov (1931a: 361), Bulgaria; Vaucher- 

 ia sessilis, Tokunaga (1933a: 26, pi. 2, figs. 17-18), Japan. 



On the basis of Zopf's observations on the vegetative stage this 

 curious organism seems more animal-like than fungoid. According to 

 Zopf, the swarmer from the overwintering spore penetrates the Vaucheria 

 filament in early spring and, once inside, becomes amoeboid. The 

 "amoebae" feed upon the chlorophyll of the host — ingesting it as solid 

 particles into the plasma — increase in size, and sometimes fuse together 

 to form an extensive netlike Plasmodium. After the Plasmodium has 

 fragmented the chlorophyll residue is expelled and each of the fragments 

 rounds off, surrounds itself with a thin wall, and forms a sporangium. 

 In each sporangium, zoospores are produced which are discharged 

 through a tube into the water, thus spreading the infection. Upon the 

 advent of unfavorable conditions later in the season the Plasmodium, 

 which may be so large as to fill the whole algal tube, divides into 

 segments ("Teilplasmodium") and from each is formed a sorus of cysts. 



It is important that observations be made on the method of infection. 

 If this occurs by encystment and by the formation of a penetration tube, 

 relationship with Woronina is strengthened; if the swarmer enters 

 as a whole, without encystment, its animal-like nature is emphasized. 



The imperfectly known Woronina aggregata Zopf {op. cit., p. 60) in 

 Mougeotia has a round cluster of from ten to twenty spore cysts which 

 discharge their zoospores through a tube. No resting spores were observ- 

 ed. Here, as in W. glomerata, the Plasmodium ingests the chlorophyll 

 and starch and expels material before encysting. What is probably 

 another species is mentioned by Zopf as occurring in Piloholus. 



