98 



PHYCOMYCETEAE 



Fig. 31. Lagenidiales, Family Olpidiopsidaceae. (A, B) Olpidiopsis vexans Barrett. 

 (A) Zoospores. (B) Zoosporangia of smooth and rough types and one mature oogone 

 with attached empty antherid. (C, D) Olpidiopsis varians Shanor. (C) Swollen tip of 

 hypha of Saprolegnia ferax (Gruith.) Thuret with three zoosporangia and one mature 

 oogone with attached, empty antherid. (D) Germination of oospore. (E) Olpidiopsis 

 luxurians Barrett, oogone and partially emptied antherid. (A and E, after Barrett: 

 Ann. Botany, 26(101) :209-238. B-D, after Shanor: /. Elisha Mitchell Sci. Soc, 

 55(1):167-195.) 



cellulose reaction upon the application of chloriodide of zinc without any 

 preliminary treatment. It is not at all certain that all the genera assigned 

 to this family really belong here. The principal genus, of about 20 species, 

 is Olpidiopsis. The zoospores are anteriorly biflagellate or the flagella may 

 be somewhat laterally attached in a groove, one directed forward (tinsel 

 type) and one posteriorly (whiplash type), as demonstrated by Couch 

 (1941). The species of this genus are strictly parasitic in the hyphae of 

 Saprolegniaceae, Pythiaceae, and various algae. One species is reported 

 in Riccia and a doubtful species in an insect. The zoospore settles on the 

 outside of the host cell and encysts with a cellulose wall. It produces a 

 slender infection tube through which the uninucleate naked protoplasm 

 enters the host. It remains naked for a while but eventually forms a 

 cellulose wall and when fully grown becomes a spherical or ellipsoidal 

 zoosporangium. An exit tube pierces the host cell wall and the zoospores 

 escape through the softened inoperculate tip. Before the exit tube opens 



