CRYPTOGAMS 



347 



Empusa Muscae, which makes its appearance in the autumn on the common house 

 fly. The mycelial filaments of this Fungus break out of the abdomen of the 

 infected fly, and give rise at their extremities to asexual conidia, which are finally 

 discharged ; they surround the fly with a white halo and spread the infection still 

 further. Sexual spores are not known to be formed by Empusa, but are found in 

 other allied genera. Both oogonia and antheridia have a similar structure, and 

 consist merely of simple tubes which swell at the ends and form resting-spores by 

 conjugation. 



Sub-Class 2. Zygomycetes 



The Zygomycetes comprise a number of the most common Mould 

 Fungi. They are saprophytic, and are found chiefly on decaying 

 vegetable and animal substances. The mycelium is unicellular in this 

 group also, and consists of profusely-branched filaments. Swarm-spores 

 are never produced, asexual reproduction being effected by non-motile 

 walled spores, which either have the form of conidia or arise endogen- 

 ously in sporangia. Sexual reproduction consists in the formation of 

 zygospores, as a result of the conjugation of two isomorphous.l gametes, 

 as in the Conjugatae among the Algae. 



The best known and most widely distributed species is Mucor Mucedo, frequently 

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



Fig. 269.— Mucor Mucedo. A unicellular mycelium with three sporangiophores, a, b, c, in different 

 stages of development. (Slightly magnified, after Kny's wall diagram.) 



dung, etc. The finely-branched mycelium ramifying in the substratum produces 

 a number of erect unbranched sporangiophores (Fig. 269). From the apex of each 

 sporangiophore a single spherical sporangium is cut off by a transverse wall, 



