LAGENIDIALES 



The order Lagenidiales comprises a group of microscopic endo- 

 biotic primarily parasitic fungi that are found in fresh and, less 

 often, marine waters. In the past the genera Myzocytium, Lagenidium, 

 Resticularia, and Ancylistes, together with Achlyogeton, were included 

 in an old order, Ancylistales, primarily on the basis of their having 

 segmented thalli. Investigation, however, has proved, as it has for the 

 chytrids, the fallibility of grouping fungi on similarity of body structure 

 alone. For example, Butler (1928) pointed out that Achlyogeton could 

 scarcely be allied to Myzocytium and Lagenidium, since it possessed 

 posteriorly uniflagellate zoospores. Furthermore, the work of Berdan 

 (1938) showed clearly that Ancylistes itself, in which nonsexual repro- 

 duction had not, prior to her work, been observed, was in fact a conidial 

 phycomycete closely allied to the Entomophthorales, to which order it 

 is now assigned (see p. 1065). 



The genus Olpidiopsis, long regarded as belonging in the Chytri- 

 diales, is considered to be allied to Myzocytium. Although Zopf( 1884: 

 173) pointed out the similarity between these two groups of fungi, it was 

 Scherffel (1925a) who showed the many resemblances that exist between 

 them and who furnished abundant evidence that Olpidiopsis could not 

 be a chytrid. The relationship to Lagenidium of the little-known marine 

 genera Sirolpidium and Pontisma was stressed by H. E. Petersen (1905: 

 482) and has been substantiated by subsequent morphological studies 

 (Sparrow, 1934c, 1936b). As a result of these changes the order Lagen- 

 idiales (the name proposed by Karling [ 1939b: 518] on the basis of 

 Berdan's work) now bears little resemblance to the Ancylistales of 

 Fischer (1892), Schroeter (1893), and Minden (1915). 



Members of the order are known primarily as parasites of algae and 

 filamentous aquatic Phycomycetes, although a few are parasitic in 

 fresh-water microscopic animals and in seaweeds. One, Lagena (Vanter- 

 pool and Ledingham, 1930), has been found parasitic in the roots of 



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