LAGENIDIALES 



987 



n 



If 





E 





// 



Fig. 80. Lagenidium 



A-C. Lagenidium brachystomum Scherffel in diatoms: A, vacuolate spo- 

 rangium showing at the left the outgrowth which will become the discharge 

 tube; place of attachment of infection tube was at extreme left tip of thallus; 

 B, portion of frustule of Synedra from which protrudes the short discharge 

 tube; zoospores are undergoing final maturation at orifice; C, mature oospore 

 in Gomphonema. D-E. Lagenidium oedogonii Scherffel: D, two vacuolate 

 sporangia with discharge tubes; E, oospore lying loosely within its container, 

 the empty tubular contributing thallus attached to it; a small empty thallus 

 with persistent infection tube is also shown. F. Lagenidium cyclotellae Scherffel 

 in Cyclotella, host with a large and a small thallus in it, empty epibiotic cysts 

 of infecting zoospores persistent. G-I. Lagenidium oophilum Sparrow in rotifer 

 eggs : G, nearly mature lobed sporangium with discharge tube protruding 

 through wall of egg; H, tip of sporangium with zoospores almost completely 

 discharged; fiagella are beginning to form on emerged spores; /, single zoo- 

 spore. 



(A-F, Scherffel, 1925a; G-I, Sparrow, 1939c) 



that the resting spore completely fills the female gametangium.) But he 

 considers the persistence of the cyst and the infection tube to be a 

 fundamental character, marking the plant as a species of Lagenidium. 

 Evidently no fertilization tube was formed by the male gametangium. 

 In the early stages of thallus development the content is typically 

 lagenidiaceous, the hyaline smooth plasma bearing refractive irregularly 

 shaped fat clods. Later, a large irregular vacuole always appears (Fig. 

 80 F). The zoospores are segregated in the parietal layer of cytoplasm 



