PHYCOMYCETES 351 



producing either a germ-tube or zoospores. Sexual repro- 

 duction unknown. 



Mucoraceae. Mycelium and sporangiophores hyaline or 

 coloured ; asexual reproduction by spores and chlamydo- 

 spores ; sexually by zygospores. Aerial. 



Rhizopus, Ehrh. Vegetative hyphae creeping, producing 

 fasciculate rhizoids that penetrate the substratum ; spor- 

 angiophores usually fasciculate, erect, coloured ; sporangia 

 globose, with a columella, many-spored, dark-coloured at 

 maturity. Zygospores formed in the substratum, con- 

 jugating branches straight; suspensors very short and 

 stout, without branchlets. Germination unknown. 



Rhizopus nigricans, Ehrenb., Nova Acta Acad. Leop.^ x. 

 i, 198, tab. xi., f. 1-7. Sporangiferous hyphae erect, in 

 fascicles of 3-10, springing from stoloniferous hyphae that 

 give off rhizoids at corresponding points ; sporangia 

 globose, blackish-olive, granular, 100-300 /x, diam., colum- 

 ella hemispherical ; spores broadly elliptical or globose, 

 grey, variable in size, 8-14 /x diam. Zygospore subglobose 

 or tun-shaped, 150-200 /m. Epispore brown, with rounded 

 warts. 



Rhizopus necans, Massee, Kew Bulletin^ 1897, p. 87, 

 i pi. Sterile hyphae, creeping, forming a thin white 

 felt; sporangiferous hyphae fasciculate, simple or forked, 

 coloured, about 2 mm. high, 20-25 /* thick, springing from 

 long, creeping stolons, which give off fasciculate rhizoids ; 

 sporangia globose, blackish-brown, smooth, about 250 \t. 

 diam., columella large, subglobose; spores subglobose, 

 minutely striate, pale olive-brown, 5-6 //. ; zygosore tun- 

 shaped, 100-120 p diam., blackish, covered with spinous 

 warts. 



