656 AQUATIC PHYCOMYCETES 



consisting when mature of a simple or branched catenulate hypha with 

 a few stubby rhizoids; usually 300-600 ;x long, consisting of 6-15 zoo- 

 sporangia or resting bodies or both, sometimes much longer and at 

 times much shorter, being composed of only one zoosporangium or 

 resting body; the swellings in the thallus connected by one-celled very 

 rarely 2-celled short isthmuses, 5-9.2 / 7-16 \x. Septations incompletely 

 formed, bumpy, pitted, or ridged. The first developed thalli forming 

 zoosporangia, the later ones zoosporangia and resting bodies, and the 

 last thalli only resting bodies. Zoosporangial development much as in 

 Allomyces or Blastocladiella simplex. Zoospores with numerous fat 

 bodies or lipoid granules, a conspicuous nuclear cap and a side body 

 (visible only when stained), posteriorly uniflagellate. First zoospores 

 emerging in a gelatinous envelope, the later ones emerging and swim- 

 ming away upon reaching the exit; swimming smoothly as in Blasto- 

 cladiella. Zoosporangia globose, subglobose, or pyriform to long ellip- 

 tic or oblong elliptic, usually oval or ovoid; 15-30 x 30-55 [l; emer- 

 gence tube 5-6 [i. thick x 10-100 jx long. Zoospores oval, 5-6.3 < 6.3-7 

 jx, cilium about 17 jx long and tail piece 6.3 jx long. Resting bodies pale 

 brown to pinkish; usually globose or subglobose, ovoid, elliptic, 

 pyriform, rarely somewhat irregular in shape. On Allomyces anomalus 

 16-51 [x when globose, 30-41 x 34-42 when subglobose; on A.javanicus 

 considerably larger, up to 63 jjl thick when globose; wall of resting 

 body 1-3 [x thick, smooth or very minutely rough; the whole spore 

 surrounded by a thin-walled case which it almost completely fills. 

 Resting body germinating by irregular cracking of the outer thick wall 

 and the emergence of a germ tube which varies from 50-several hundred 

 u. in length. Resting body zoospores uniciliate when discharged and 

 capable of a little feeble movement, encysting almost immediately near 

 the emergence pore in an irregular mass. Cysts spherical, 5.4-6.4 u. thick. 

 After a rest period of about 2 hours germinating to form four uniciliate 

 gametes which emerge through a pore to fuse in pairs, gametes 3 x 4.4- 

 4.7 jjl. Zygotes biciliate, 3.5-7.6 [x. Germinating and penetrating the 

 host to form a zoosporangial thallus" (Couch, he. eit.). 



Parasitic in Allomyces anomalus, in soil; capable of infecting Allo- 

 myces arbuscula, A.javanicus, A. moniliformis, and Blastocladiella sim- 

 plex, United States. 



