CHYTRIDIALES 59 



at maturity entirely free from one another and are not aggre- 

 gated in any manner (Fig. 4, h). They are finally freed by the 

 disorganization of the host tissue, and are disseminated in the 

 soil water. Under favorable conditions each spore splits open 

 and germinates by a single zoospore, which swims for a time 

 (Chupp 1917: 425) with a single ciHum attached to the forward 

 end (Fig. 2). It finally comes to rest, and, having penetrated 

 the host, exists in the cell in the non-ciliate amoeboid state. 

 Woronin described the free-swimming spore as also amoeboid. 

 Germination has been seen by few investigators and the accounts 

 are contradictory (see U. S. Dept. Agr. Tech. Bui. 181, p. 7, 1930). 



An unconvincing account of the life history of the organism, 

 widely at variance with all previously published results, has been 

 presented recently by Jones (1928: 313). He states that the 

 spore in germination frees one to twenty ciHate cells and that 

 these undergo a sexual fusion in pairs. 



The genus has been used from the beginning as a dumping 

 ground for doubtful species. It is pointed out above that PI. 

 alni and PI. elaeagni were based on the legume tubercle organism 

 or related species. Several species, PI. tJitis, PL californica, PI. 

 theae, and PI. orchidis are now known to have been founded 

 merely on the products of cell disorganization. More recently 

 PI. halophilae Ferdinandsen & Winge (1913) has been described 

 from the petioles of Halophila ovalis; a species has been described 

 on sugar cane as PI. vascularum Matz by Matz (1920) Bourne 

 (1922) and Cook (1924; 1929); PZ. tabaci Jones (1926) has been 

 discussed in connection with tobacco mosaic; and at least two 

 other species, PI. ficus-repentis Andreucci (1926) and PI. humuli 

 Nicholls (1924) have been pubhshed. In none of these cases 

 has sufficient detail of Ufe history, morphology, and cytology 

 been provided to justify their inclusion in this genus as more 

 than doubtful forms. 



2. Tetramyxa Gobel (1884). 



The genus was founded on the single species T. parasitica 

 G5bel parasitic on Ruppia rostellata, a member of the pond weed 

 family. The organism causes the formation of peculiar whitish 

 galls on all parts of the plant except the roots. The genus is 

 characterized by the tendency of the spores to cling together in 

 tetrads. Sometimes they are found in dyads, or as single spores. 

 More rarely large binucleate spores occur. 



