UNIFLAGELLATAE 



CHYTRIDIALES 



The discovery of the fungous nature of the aquatic chytrids and 

 their recognition as a taxonomic entity are due for the most part 

 to the researches of Alexander Braun. It is clear that as early as 1846 

 Braun (1856a: 22) had observed chytrids on the fresh-water algae 

 Hydrodictyon and Stigeoclonium and was aware of their parasitic role. 

 In his Betrachtungen iiber die Erscheinung der Verjiingung in der Natur 

 (1851), he formally established the genus Chytridium with one species, 

 C. ol/a, which was parasitic on the oogonia of Oedogonium. To be 

 sure, there were descriptions in the literature prior to Braun's paper of 

 organisms now known to be true chytrids (species of Synchytrium, 

 Physoderma, and Micromyces), but their affinities and, indeed, in some 

 instances, their parasitic nature were not understood. Gross (1851), 

 in connection with a curious account of supposed polymorphism and 

 metamorphism in lower plants and animals, described and figured a 

 chytrid identifiable with Polyphagias euglenae. Thwaites (1846-47), 

 Shadbolt (1852), and other early algologists gave the term "astero- 

 spheres" to spiny spheres found by them in vegetative cells of Conju- 

 gatae. As late as 1860 Pringsheim interpreted the zoospores of an endo- 

 biotic chytrid (now known as Pringsheimiella) parasitic on a sterile 

 Achlya as the antherozoids of the host, and other examples might be 

 cited. With the publication of Braun's classic series of papers on Chy- 

 tridium (1855a, 1855b, 1856a, 1856b), the small group became well 

 established and their true nature generally recognized. 



Included in Braun's Chytridium was one supposed chytrid, C. sapro- 

 legniae, whose zoospores were not observed and which probably was 

 not related to his other species. It came to be identified with fungi 

 which were observed by Niigeli (1846), Cienkowski (1855), and Cohn 

 (1853, as Peronium aciculare) and which were all probably species of 

 Olpidiopsis. Subsequently a number of other one-celled aquatic fungi 



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