100 



THE SIMPLE HOLOCARPIC BIFLAGELLATE PHYCOMYCETES 



Serbinow, J. 1899. Trav. Soc. Nat. Petrograd 30: 255. Tokunaga, Y. 1934. Trans. Sapporo Nat. Hist. Soc. 13: 



Skvortzow, B. W. 1925. Arch Protistk. 51: 428. 1927, Ibid. $27. 



57 : ~ 0i - Turner, W. B. 1892. Kongl. Svensk. Veten.— Akad. Hand. 



Sorokin, N. 1870. Ann. Sci. Nat. 6 ser. 4: 63. 25 5. j 



Sparrow, F. K. 1932. Mycologia 24: 268, 289. 1933, Ibid. Valkanov, A. 1931. Arch. Protistk. 73: 361. 



2.5: 513. 1942, Ibid. 34: 113 Vuillemin, P. 1908. Prog. rei. Bot. 2: 1. 

 Stein, F 1851 Zertschr. W.ss. Zool. 3: 475. Wettstein, R. 1935. Handb. der Svstemat. Bot. 4 ed. Leip- 

 . 18o4. Die Intusionsthiere unci lhre Entwickelungs- 



geschichte. Leipzig. 



zig. 



-. 1859. Der Organismus der Infusionsthiere. Abt. Wildeman, E. de. 1895a. Ann. Soc. Micro. Beige 19: 63. 

 1-1(55 189 1895b, Ibid. 19: 215. 



Tavel, F. 1892. Vergleichende Morphologie der Pilze, -. 1896. Bull. Soc. Roy. Bot. Belgique 35: 7. 



Jena. 

 Thompson, G. E. 1934. Mycologia 26: 118. 



Wolk, P. C. 1913. Mycol. Centralbl. 3: 153. 

 Zopf, W. 1897. Hedwigia 18: 94. 



Chapter VII 

 Phylogeny 



Discussions of phylogeny at any given period of 

 time must obviously be based on existing knowledge 

 and data relative to the group of organisms in ques- 

 tion. Relationships which thus seem obvious at pres- 

 ent may be completely invalidated by future studies 

 and discoveries. Therefore, very few definite conclu- 

 sions can be drawn at present about the origin and 

 evolution of these holocarpic, biflagellate Phyeomy- 

 cetes as a whole because so little is known about the 

 critical developmental stages of many of the genera 

 and species. The present discussion will accordingly 

 be confined to pointing out similarities and differ- 

 ences between these fungi, the lower organisms and 

 higher fungi witli which they appear to be related. 

 Since it is not certain that all of the families de- 

 scribed in the previous chapters constitute a natural 

 phylogenetic series of closely related species, dif- 

 ferences in origin and relationship are to be ex- 

 pected. As has been briefly noted before, these rela- 

 tionships involve principally the Proteomyxa or 

 Monadineae, Plasmodiophorales, Saprolegniales, 

 and Peronosporales and are based on similarities or 

 differences in thallus structure, type of development, 

 relative lengths and position of flagella, diplanetism, 

 presence of cellulose in the cell walls, and type of 

 sexual reproduction. Present day evidence suggests 

 very strongly that most of these holobiflagellomy- 

 eetes are either remotely or closely related to the 

 higher Phycomycetes. However, it is not clearly 

 evident whether they are primitive or reduced and 

 degenerate, and many of the controversies on phylog- 

 eny in the past have centered on these questions. 

 While the views of the early mycologists in this re- 

 spect do not relate to groups as specific as those 

 included in these so-called holobiflagellomycetes, 

 they nonetheless apply here in a general sense. 

 DeBary ('81, '84), Tavel ('92), Gaumann ('26), 

 Gaumann and Dodge ('28), Mez ('29), Wettstein 

 ('35) among others regarded most of the biflagellate 

 species as reduced and degenerate oomycetous fungi 

 resulting from their assumption of a parasitic mode 

 of life. On the other hand, Dangeard ('86, '06), 

 Lotsy ('07), Vuillemin ('08), Atkinson ('09), 

 Cavers ('15), Scherffel ('25), Fitzpatrick ('30), 

 Cook ('28), Bessey ('42), and others believed that 



they are primitive and represent an ascending evo- 

 lutionary line. Lotsy and Bessey suggested that 

 they may have been derived from the Isocontae and 

 unicellular Heterokontae, respectively. Atkinson did 

 not attach much significance to the number of flagella 

 and derived them from the Chytridiales. Dangeard, 

 Cavers, Scherffel, and Cook, however, believed that 

 together with the Chytridiales they originated from 

 the zoosporic Monadineae or Proteomyxa. 



The evidence bearing on the origin and relation- 

 ships of these holobiflagellomycetes will now be con- 

 sidered in greater detail. The provisional family, 

 Woroninaeeae, interpreted as a convenient dumping 

 ground or a heterogeneous collection of genera which 

 are quite probably unrelated, appears to be the most 

 primitive and stands somewhat apart from the other 

 families because its vegetative thallus is reported to 

 be plasmodial in structure and mode of nutrition. 

 As noted before, in IVoronina the plasmodium 

 cleaves into segments which are transformed directly 

 into zoosporangia or resting spores. These struc- 

 tures may be united into compact sporangio- and 

 cystosori, respectively, in TV. polycystis, while in 

 W. glomerata they lie comparatively loose and free. 

 The striking similarity in type of development of 

 these species to that of the Plasmodiophorales is 

 obvious. Zopf ('94), Maire and Tison ('11), and 

 Winge (13) and others early recognized this simi- 

 larity and stressed the relationship of W. polycystis 

 to Ligniera and other genera of the Plasmodio- 

 phoraceae. This relationship was further empha- 

 sized by Ledingham's ('33, '39) and Couch's ('39) 

 discoveries of Polymyxa and Octomyxa, respective- 

 ly. The latter genus, particularly, is almost identical 

 in life cycle to W. polycystis, as was stressed by the 

 present writer ('42) in his book on the Plasmodio- 

 phorales. Sparrow ('42) included Woronina in the 

 latter order and discarded the family name Woroni- 

 naeeae altogether. As has been stated already, future 

 studies may possibly prove that W. polycystis is a 

 species of the Plasmodiophorales, but so far as is now 

 known, it differs in several respects from the valid 

 members of this order. In the first place, it is not 

 definitely known whether the zoospores are iso- or 

 heterocont and whether the flagella are lateral or 



