CHAPTER XIX 



CONJUGATING FUNGI PHYCOMYCETES ' 



The comparatively small order of fungi known as the 

 Phycomycetes has been subjected to more exact examination 

 and clearer definition than when Berkeley called it Physomycetes 

 in 1857, and limited it by the definition of "fertile cells, 

 bladder-shaped, scattered on the threads which are not com- 

 pacted so as to form a distinct hymenium. Sporidia in- 

 definite, formed from the protoplasm of the cells." It will be 

 observed that this diagnosis only takes cognisance of the 

 superficial, and asexual, reproduction by gonidia, produced 

 within sporangia, the latter being scattered over the threads, 

 as in typical forms of Mucor. 



Technically, as at present recognised, the Phycomycetes are 

 characterised by a vmicellular mycelium, often parasitic on 

 plants or animals, sometimes saprophytic, developed in the air 

 or in water. Reproduction sexual or asexual. Sexual by 

 oogonia and antheridia, or by conjugation, producing zygospores. 

 Asexual by means of gonidia or zoospores. Many of them 

 resemble, more or less, the moulds in external appearance, 

 having conspicuous hyphae, arising from a procumbent creep- 

 ing mycelium — but that the latter threads are without septa, 

 and the former may either produce sporangia or naked gonidia. 

 Moreover, they are fm-ther removed from the moulds by 

 possessing, in addition to the conspicuous agamic reproduction, 

 a true sexual method by means of oogonia fertilised by 

 antheridia, or by zygospores resulting from conjugation of 

 specialised branches. 



Undoubtedly there is considerable variability in the 

 external features of the different families constituting this 



