PHYLLOSIPHON Kuhn 1878, p. 24 



This genus is parasitic in the tissues of the common Jack-in-the- 

 pulpit, Arisaema triphyllum (L. ) Schott. The thallus consists of a 

 much twisted and closely compacted coenocytic tubular filament 

 with numerous oval chloroplasts and nuclei. The alga brings about 

 the disintegration of the host tissues and a destruction of the 

 chlorophyll so that large yellow patches develop. Food reserve is 

 in the form of either starch or oil. The only known method of 

 reproduction is by the formation of numerous aplanospores in the 

 tube which, upon being liberated, generate new coenocytic filaments 

 directly. 



Phyllosiphon Arisari Kiihn 1878, p. 24 



PI. 69, Figs. 1-3 



Characters as described for the genus; tubes dichotomously 

 branched, ramifying among the tissues of the host plant and 

 producing discolored areas; tubes 25-35/a in diameter, 60 fi in 

 diameter during aplanospore production. 



On blades and stalks of Jack-in-the-pulpit. Wis. (Swingle). 



FAMILY VAUCHERIACEAE 



Thallus long, much-branched, coenocytic tubes, sometimes pos- 

 sessing horizontal, downwardly directed, and vertical sex-organ- 

 bearing branches; chloroplasts numerous ovate or circular discs 

 embedded in a thin sheet of cytoplasm along the wall and about 

 large vacuolated central regions; pyrenoids lacking; reserve food 

 either oil or ( less often ) starch; reproduction by large multiflagellate 

 zoospores cut off from the ends of branches, by akinetes, or by 

 eggs and antherozoids, the gametes being produced in special sex 

 organs. 



Key to the Genera 



Regularly branched dichotomously and frequently 



constricted; sex organs terminal Dichotoinosiphon 



Irregularly branched (sometimes sparsely so), not constricted; 

 sex organs lateral on the main filament 

 or terminal on lateral branches Vaucheria 



DICHOTOMOSIPHON Ernst 1902, p. 115 



A multinucleate siphon, forming attached, felt-like masses on the 

 bottom of aquatic habitats, or rarely subaerial on damp soil; branch- 

 ing usually dichotomous with frequent constrictions at the base of 

 the branches; chloroplasts numerous small discs; pyrenoids lacking; 

 sexual reproduction oogamous, the sex organs borne in corymb-like 



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