100 PHYCOMYCETEAE 



temporary resting place for the species in which resting spores, either 

 sexually or parthogenetically produced, are unknown while Sparrow 

 (1943) uses this name for the forms with parthogenetically produced 

 resting spores. They occur in algae or fungi. 



Peter senia was described by Sparrow (1934) for two species parasitic 

 in marine Florideae and one species in Saprolegnia, which differ from 

 Olpidiopsis in the production of lobed or tubular zoosporangia, mostly 

 with more than one discharge tube, and for which, so far, no resting 

 spores are known. In Pythiella (Couch, 1935) the primary zoospores are 

 without flagella and creep out through the mouth of the exit tube where 

 they encyst and after about an hour emerge as zoospores of the secondary 

 type, with the two flagella laterally attached. The female cell produces a 

 distinct egg with periplasm and the male cell fertilizes it through a short 

 conjugation tube. It is possible that this genus represents a very much 

 reduced form of Pyihium. The only known species is parasitic in the 

 hyphae of species of Pythium. Pseudosphaerita resembles Sphaerita of the 

 Olpidiaceae. It is imperfectly known and needs further study. 



Family Sirolpidiaceae. In this as in the foregoing family the fungus 

 lies free within the host cell and produces a cellulose wall. Usually, how- 

 ever, this cell elongates and becomes divided by cross walls into several 

 zoosporangia which disarticulate, in Sirolpidium, or remain tubular, 

 sometimes shortly branched, with cross walls at maturity but not dis- 

 articulating, in Pontisma. Resting spores are not known in either genus. 

 Both are parasitic in marine algae, the former in Bryopsis and Cladophora, 

 the latter in the red alga Ceramium. In both genera the laterally biflagel- 

 late zoospores are produced in the zoosporangia and escape fully formed 

 through an inoperculate exit tube. Karling (1942) places Petersenia in 

 this family because of its elongated, tubular, or lobed cell body. Its type 

 species was originally described as a species of Pleotrachelus, of the 

 Olpidiaceae, but differs from that in the biflagellate zoospores. 



Family Lagenidiaceae. This family was originally named Ancylisti- 

 daceae, but with the discovery by Miss Berdan (1938) that the genus 

 Ancylistes really belongs in the Entomophthorales, the present designa- 

 tion was given by Karling (1939). In this family the zoospores are mostly 

 of the secondary type, the primary type being rare. The contents of the 

 zoosporangium are set free through an exit tube into a vesicle in which 

 the zoospores attain their final form and then escape by bursting the 

 vesicle membrane. They encyst and germinate on the outside of the host 

 cell and form a slender infection tube at whose apex a short or long, simple 

 or branched, coenocytic plant body is formed. This may remain non- 

 septate in Lagcna or septate with cylindrical segments in Lagenidium or 

 constricted at the septa into bead-like segments as in Myzocytium. Each 

 segment may become a zoosporangium or a gametangium. Adjacent seg- 



