CRYPTOGAMS 



383 



The behaviour of these two species can be regarded as primitive, the uninucleate 

 oospheres of the first -named forms having been derived from the multinucleate 

 condition. Albuijo tragopoyouis occupies an intermediate position in that its 

 oosphere is at first multinucleate, but later contains only one female nucleus, tin- 

 others having degenerated. The superfluous nuclei in the oogonia and antheridia 

 may be regarded as the nuclei of gametes which have become functionless, and are 

 comparable with the superfluous egg-nuclei of certain Fucaceae. The oospores 

 either produce a mycelium directly or give rise to swarm-spores. 



FIG. 321. Fertilisation of the Peronosporeae. 1, 1'eronospora 

 parasitica. Young multinucleate oogonium (og) and anther- 

 idiuin (an). %, Allunjo Candida. Oogonium with the central 

 uninucleate oosphere and the fertilising tul>r (</) of the 

 anthcridiuni which introduces the male nucleus. 3, The sam>-. 

 Fertilised egg-cell (o) suiTounded by the periplasm (/.). (After 

 \V MiK.K. x 666.) 



FIG. 322. Rhizopiis nigricans ( Mm-or sto- 

 lonifer). Portion of tin- niyceliuin with 

 three sporangia ; that to the right is shed- 

 ding its sjwres and shows tint jiersisti-nt 

 hemispherical columella. (x 38.) 



Order 2. Zygomycetes 



1. The Mucorineae ( 55 ) comprise a number of the most common Mould Fungi. 

 They are saprophytic, and are found chiefly on decaying vegetable and animal 

 substances. Asexual reproduction is effected by non-motile, walled spores, which 

 either have the form of conidia or arise endogenously in sporangia. Sexual 

 reproduction consists in the formation of zygospores, as a result of the conjugation 

 of two equivalent coenogametes. 



One of the most widely distributed species is Mucor Mucedo, frequently found 

 forming white fur-like growths of mould on damp bread, preserved fruits, dung, 

 etc. Mucor stolonifcr (^lihizopus nigricans}, with a brown mycelium, occurs on 

 similar substrata. The spherical sporangia are borne on the ends of thick erect 

 branches of the mycelium (Fig. 322). From the apex of each sporangiophore a 

 .single spherical sporangium is cut off by a transverse wall, which protrudes into 



