THE BASIDIUM FUNGI (BASIDIOMYCETES) 255 



life processes they are of the greatest importance, since they 

 are instruments of decay and soil enrichment, and bear an im- 

 portant relation to various industries. As producers of diseases 

 of plants, animals, and men, they have great significance. 



Phycomycetes are sometimes saprophytic and sometimes 

 parasitic. As saprophytes they are instruments of decay, and 

 as parasites they often kill their hosts and then as saprophytes 

 disorganize them. The simpler phycomycetes, as bread mold, 



Fig. 213. Nest fungi growing in soil in which is decaying wood 



"Within the cup-like plants are the egg-like hodies which contain the spores. 

 Natural size 



reproduce themselves by asexual spores and by forming zygo- 

 spores, as do some of the green algse. One of the more com- 

 plex forms, water mold, lives in the vs^ater and reproduces by 

 means of zoospores ; it also forms oospores by means of special 

 sex organs. Sometimes its oospores are produced without fer- 

 tilization. Such forms as the downy mildew of the grape are 

 parasites. They bear conidia, or sporangia-like bodies, upon the 

 leaves of theii" hosts, and produce oospores within these leaves. 

 Ascomycetes have conidia, but are distinguished by the fact 

 that some of their spores are formed in sacs at the tips of 

 hyphse. These sacs are in open cups, as in MorcheUa, Peziza, 

 and Sclerotinia; or inclosed, or almost so, as in the lilac mil- 

 dew. Some forms (^PenicUUum and yeasts) seem to have lost 

 part of the usual ascomycete life cycle. The life habits of 



