MU COR ALES 



271 



single row of spores (six in D. cornula van Tieg., two in D. 

 americana Thaxter) which at maturity have the aspect of a chain 

 of conidia ckie to the dissolution of the sporangial wall; 

 zygospores formed in an anomalous manner and always in close 

 connection with the host hypha; at maturity partly enclosed by 

 finger-like processes which arise from one of the gametangia 

 (Fig. 99). 



The points of dissimilarity between the two above named 

 species, as indicated by the original descriptions, are enumerated 

 by Thaxter (1895: 513). More recently Bainier (1906: 213) 



Fig. 99. — Diapira americana Thaxter. (a) Sporangiophore with spherical 

 sporangium-bearing heads and sterile sharp-pointed tips, {h) Optical section 

 of a single such head showing the peculiar budding sterigmata terminated by 

 sporangia, (c) Sterigma bearing two sporangia, each containing two spores. 

 {d) Sporangiophore of Mucor attacked by hyphae of Dispira; the latter septate 

 near host hypha to form pairs of gametangia. (e) Gametangia and zygospores 

 in various stages of development. (/) Single mature zygospore surrounded 

 in part by a rosette of finger-like processes arising from one of the gametangia. 

 (After Thaxter 1895.) 



has redescribed D. cornuta and states that the two species are 

 identical. A third species, D. circmata Elliott (1926) has been 

 described rather inadequately from the asexual stage only. 



The sexual process as described by Thaxter for D. americana, 

 may be briefly reviewed. From the slender creeping vegetative 

 hyphae of the parasite short lateral branches are put out which 

 come in contact with the host hypha and attach themselves to it 

 as suckers. Each sucker then becomes septate into two cells 

 which then function as gametangia in zygospore formation. The 

 enveloping finger-like processes always arise from that game- 

 tangium which joins the host. 



Although in Dispira the chains of spores developed at the 

 tips of the fertile hyphae have not been demonstrated clearly 



