82 PHTCOMTCETEAE 



observed. Twelve or more species. Only genus known Coelomomyces 

 (Keilin, 1921; Couch, 1945b; Couch and Dodge, 1947). (Fig. 23H, I.) 



Family Blastocladiaceae. The vegetative portion of the plants of 

 this family consists of a more or less extensive system of tapering and 

 branching rhizoids and of a globular or clavate external portion from 

 which may arise directly the sporangia and gametangia or a system of 

 branches on which these organs are borne. In Allomyces the hyphae are 

 more nearly uniform, without a broad basal portion, and are frequently 

 constricted here and there. At these points usually occur coarsely perfo- 

 rate "pseudosepta." Three or more genera are recognized in this family, 

 which may be distinguished as follows: 



Blastocladia: plant body with a simple, lobed or branched basal portion, often 

 with secondary axes. Zoosporangia with a single apical exit papilla. Alter- 

 nation of sporophytes and gametophytes unknown. 



Blastocladiella (including according to Couch and Whiffen (1942) Clavochytrium 

 and Sphaerocladia) : plant body a spherical vegetative structure bearing 

 rhizoids at the base or on all sides, or more or less clavate, becoming directly 

 a reproductive organ or bearing at its apex the single reproductive organ. 

 Alternation of generations demonstrated in some species. Discharge papillae 

 one or several. 



Allomyces: plant body a cylindrical basal segment giving rise, usually di- 

 chotomously, to cylindrical, often constricted, branches with pseudosepta. 

 Discharge papillae usually more than one. Alternation of sporophytes and 

 gametophytes known in some species. 



Blastocladiella. In Blastocladiella stuhenii Couch and Whiffen (1942) 

 the plant body of the sporophyte is spherical, with tapering, much- 

 branched rhizoids emerging at all sides. It bears a thin-walled zoospo- 

 rangium with one to several discharge tubes or a dark, thick-walled, 

 resting sporangium which produces swarm cells that give rise to indis- 

 tinguishable male or female gametophytes similar to, but smaller than, 

 the sporophytes. The emerging gametes are equal in size and cannot be 

 distinguished by color. They fuse in pairs and at once produce the 

 sporophytes. In B. variabilis Harder and Sorgel (1938) the sporophyte is 

 cyhndrical, bearing at its base much-branched rhizoids and at its apex 

 either a thin-walled zoosporangium or a thick-walled resting sporangium. 

 The zoospores from the former give rise to sporophytes again but those 

 from the latter (planonts) give rise to similar gametophytes, each with a 

 single clavate gametangium, orange-colored in the male and colorless in 

 the female gametophyte. The biflagellate zygote gives rise at once to a 

 sporophyte. Five other species are distinguished. In B. stomophila (Couch 

 and Cox) Couch and Whiffen only thin-walled zoosporangia have been 

 obser\'ed. In B. simplex Matthews and two other species both zoospo- 

 rangia and resting sporangia are produced, but the zoospores from the 

 latter reproduce sporophytes, no gametophytes having been recognized. 



