106 



THE SIMPLE HOLOCARPIC BIFLAGELLATE PHYCOMYCETES 



were of the opinion that it embraces only reduced 

 and degenerate species which have arisen as the re- 

 sult of submersed parasitism — a viewpoint which 

 has been revived by Gaumann, Gaumann and Dodge, 

 and Mez. However, the majority of students of this 

 group, including Schroeter ('97), Minden ('11), 

 Atkinson ('09), Cavers ('15), Scherffel ('25), Cook 

 ('28), and Fitzpatrick ('30), believed that this fam- 

 ily constitutes an ascending series which has given 

 rise to various groups of the Phycomyeetes. Atkin- 

 son related Lagenidium to the chytrid Polyphagia 

 and postulated that the Lagenidiaceae may have 

 originated from certain species of the Rhizidiaceae 

 and in turn led to the development along more or 

 less parallel lines to the higher Oomycetes and Zygo- 

 mycetes. In this connection it may be noted that 

 many years earlier Zopf ('84, p. 190) suggested 

 that Rhinidiomyces apophysitis may be a type of 

 species which relate the Rhizidiaceae with the An- 

 eylistaceae (Lagenidiaceae) and Pythiaceae. While 

 Cavers believed that the Phycomyeetes originated 

 in the Proteomyxa, he thought that the Ancylistineae 

 (Lagenidiaceae) are derived from the Chytridiales 

 and lead to the Peronosporaceae. Scherffel, as noted 

 before, believed that the Lagenidiaceae developed 

 from Ectror/ella- and Olpidiopsis-like ancestors and 

 is connected with his P^fc/am-Peronosporales series 

 through Pythiogeton (diagram 1). Lagenidium Cy- 

 lotellae, in his opinion, is a connecting link between 

 Ectrogella and the Lagenidiaceae (Ancylistineae). 

 Cook regarded the Aneylistaceae (Lagenidiaceae) 

 as intermediate between the Chytridiales and Oomy- 

 cetes proper and believed that it may have given 

 rise on one hand to the Saprolegniaceae through the 

 Blastocladiales and Leptomitaceae, and on the other 

 band to the Peronosporaceae through the Pythiaceae 

 and Albuginaceae (diagram 3). Inasmuch as the 



konobllphandmtO* 



Diagram 3. The origin of the Aneylistaceae (Lagenidia- 

 ceae) and its relation to the higher Oomycetes, according 

 to Cook, 19->8. 



zoospores of the Blastocladiales are uniflagellate 

 and both gametes are motile, it is difficult to conceive 

 how this order has arisen from the Lagenidiaceae. 



Present day evidence indicates that the Blastocla- 

 diales may have originated directly from the Chy- 

 tridiales. Sparrow ('42) placed the Lagenidiaceae 

 at the top of the Lagenidiales next to the Perono- 

 sporales, suggesting thereby that it may have origi- 

 nated from the Olpidiopsidaceae and Sirolpidiaceae. 

 Bessey ('42) likewise derived it from the Olpidiop- 

 sidaceae and suggested (diagram 2) that it may have 

 given rise in a more or less direct line to the Pythia- 

 ceae, Albuginaceae and Peronosporaceae on one 

 hand and to the Leptomitaceae and Saprolegniaceae 

 on the other. 



Having reviewed briefly the various views on the 

 phylogeny of the Lagenidiaceae, let us now examine 

 the data on which they are based. In size and shape 

 the thallus of some species of this family resembles 

 the mycelium of the filamentous Oomycetes, but in 

 other species it is like that of the Olpidiopsidaceae. 

 These characters, therefore, do not always afford a 

 fundamental basis of relationship. Fischer and Lot- 

 sy, nevertheless, used them and the holocarpic nature 

 of the thallus as the chief grounds for including the 

 Lagenidiaceae in the sub-order Mycoehytridineae, 

 following the Olpidiaceae and Synchytriaceae. At 

 that time few species with extensive, filamentous, 

 mycelioid thalli were known so that the oval, ellip- 

 soid or tubular, irregular, vermiform and elongate 

 shapes were regarded as more characteristic of the 

 family. Since then species like Lagenidium marcha- 

 lianitm, L. Closterii, L. giganteum, etc., have been 

 described, the thalli of which can hardly be distin- 

 guished from the mycelium of Pythium. Conversely, 

 reduced, holocarpic, relatively short, vermiform and 

 unbranched thalli may rarely occur in Pythium, 

 Achlya, etc., so it is obvious that within certain limits 

 size, shape, and extent of thallus are not always of 

 fundamental value in judging affinity. 



In methods of zoosporogenesis and the behavior 

 of the zoospores after emerging, several lines of 

 relationship are suggested. The majority of species 

 show distinct pythiacous tendencies because the 

 primary swarm period is suppressed and lacking. 

 The protoplasm emerges from the sporangium and 

 undergoes cleavage on the outside with or without 

 a surrounding vesicular membrane. Lagenidium 

 Oedogonii and Lagenidium sp. Couch, on the other 

 band, exhibit a combination of Pythium, Sapro- 

 legnia and Achlya characteristics. In the former 

 species the zoospores may be formed extramatri- 

 cally in a vesicle as in Pythium or within the spo- 

 rangium and then encyst at the mouth of the exit 

 tube after emerging as in Achlya. In the latter spe- 

 cies they are formed in a vesicle but after swim- 

 ming about for a short while they encyst. Within 

 one to three hours, they emerge from the cysts and 

 become motile again as in Saprolegnia. In L. Cyclo- 

 tellae, however, the zoospores are formed in the same 

 manner and behave like those of Olpidiopsis and 

 some species of Ectrogella. 



In shape, structure, position of the flagella, and 

 type of swimming the zoospores of most species are 

 essentially like those of Pythium and the secondary 



