Chapter VHI 

 PHYLUM OPISTHOKONTA 



Phylum 4. OPISTHOKONTA, phylum novum 



Chytridieae de Bary in Bot. Zeit. 16, Beil. 96 (1858). 



Family Chytridieen de Bary and Woronin (1864). 



Family Chytridiaceae Cohn in Hedwigia 11: 18 (1872). 



Chytridineae Schroter in Engler and Frantl Nat. Pflanzenfam. I Teil, Abt. 1 : 

 62 (1892). 



Series (Reihe) Archimycetes (Chytridinae) A. Fischer in Rabenhorst Kryp- 

 tog.-Fl. Deutschland 1, Abt. 4: 11 (1892). 



Suborders Chrytidiineae and Monoblepharidineae Engler in Engler and Prantl 

 Nat. Pflanzenfam. I Teil, Abt. 1: iii, iv (1897). 



Order Chytridineae Campbell Univ. Textb. Bot. 152 (1902). 



Classes Archimycetae and Monoblepharideae Schaff'ner in Ohio Naturalist 9: 

 447,449 (1909). 



Class Archimycetes Gaiimann Vergl. Morph. Pilze 15 (1926). 



Uniflagellatae Sparrow Aq. Phyc. 21 (1943). 



Parasites and saprophytes of simple structure (filamentous, of uniform diameter 

 or tapering; or unicellular, with or without rhizoids, i. e. tapering filamentous out- 

 growths), with cell walls of chitin, containing no cellulose; producing motile cells 

 with solitary posterior acroneme flagella. Type, Chytridium Olla Braun. From 

 6tt[o9ioc;, rearward, and KOVT6q^oar. 



Chytrid is the English form of the generic name Chytridium, from Greek )(UTp(<;, 

 a jug. Braun (1856) applied this name to a colorless unicellular organism found 

 attached to green algae whose cells are penetrated by rhizoids which draw food from 

 them and kill them. By chytrids we mean organisms of body types of the general 

 nature of that of Chytridium. All such organisms were formerly treated as a single 

 taxonomic group. Couch (1938, 1941) showed that the organisms of chytrid body 

 type form three markedly distinct groups distinguished by types of flagellation. The 

 proper chytrids, those which legitimately constitute a taxonomic group, are marked 

 by swimming cells with solitary posterior acroneme flagella, and further by lack of 

 cellulose in the cell walls. The group thus marked includes, beside organisms of 

 chytrid body type, a few organisms of the filamentous body type of the typical fungi. 



The cytoplasm of members of this group is described as peculiarly lustrous and 

 as containing shining globules. In mitosis (seen repeatedly, as by Dangeard, 1900, 

 Stevens and Stevens, 1903, Wager, 1913, and Karling, 1937), the sharp-pointed 

 spindle forms within the intact nuclear membrane. Some observers have seen centro- 

 somes at the poles. The nuclear membrane disappears toward the end of the process. 



The formation of motile cells (zoospores and sometimes gametes) occurs in en- 

 larged cells. In these cells there are repeated simultaneous nuclear divisions. After 

 the last of these, uninucleate protoplasts, each one containing, ordinarily, one of the 

 above-mentioned shining globules, are separated by cleavage. On each of these 

 protoplasts a flagellum grows from the cell membrane at the point nearest that part 

 of the nucleus which represents a pole of the previous mitotic spindle. Among the 

 Blastocladiacea, the nucleus lies against the cell membrane and the flagellum appears 

 to spring from a granule within it (Cotner, 1930; Hatch, 1935). Similarly, in Clado- 



