1014 AQUATIC PHYCOMYCETES 



budlike processes on the mycelium of Pythium under certain environ- 

 mental conditions. Some workers (see Drechsler, 1925) have considered 

 these to be intimately connected with nonsexual reproduction, but this 

 is not true in all instances (Sparrow, 1931a). Irregularities of the 

 mycelium and twisted complexes of the hyphae are exhibited by a 

 number of species of Phytophthora (Petersen, 1910; Kanouse, 1925; Ito 

 and Nagai, op. cit.) and by Zoophagus (Prowse, 1954b). 



Some aquatic species of Pythium parasitic on algae (Sparrow, 1931a, 

 1931b) bear clusters of clavate or sickle-shaped appressoria wherever 

 the tips of the hyphae come into contact with the substratum. These 

 become cemented to the algal wall by concave hyaline adhesion discs ; 

 from the face of each of these anchoring organs a tube develops which 

 penetrates the algal wall (Fig. 86 K, p. 1030). Inside, a hypha of typical 

 diameter is produced. Similar appressoria may be formed within the 

 alga. They are also present in at least one species of Pythiogeton (Drechs- 

 ler, 1932). Another type of specialized mycelial structure occurs in 

 Zoophagus and is a lateral outgrowth adapted to capturing rotifers. In 

 Z. insidians (Sommerstorff, 1911; Mirande, 1920; Arnaudow, 1921, 

 1925; Gicklhorn, 1922; Sparrow, 1929; Prowse, 1954b) the extensive 

 hyphae bear numerous short upright peglike branches, the tips of 

 which secrete a mucilaginous material (Fig. 85 A, p. 1029). The rotifer 

 coming into contact with these tips becomes stuck and its body even- 

 tually is penetrated by a hyphal outgrowth. The trapping organs, as 

 such, do not develop in culture but there, rather, assume the structure 

 of lateral branches. In Z. tentaclum (Karling, 1936c) the lateral branch 

 bears an even more specialized capturing device. It consists of from one 

 to five narrow tentacles formed at the apex of the branch. No mucilagi- 

 nous secretion could be demonstrated in this particular species (Fig. 85 H). 



Well-defined thick-walled chlamydospores have been reported in 

 Pythium (Dissmann, 1927; Matthews, 1931; Goldie-Smith, 1952). 



REPRODUCTION 



Nonsexual Reproduction 



In the aquatic species of the Pythiaceae zoosporangia and zoo- 

 spores are produced. The sporangia are of three main types: (a) an 



