REPRODUCTION AND DISPERSAL 



8*3 



turgor, whereupon the escaping water tears loose the sporangium and expels it with 

 the enclosed spores for some distance. In a somewhat similar fashion are expelled 

 the conidia of Entomophthora and the ascospores of Ascobolus and of Peziza repanda. 

 In the ergot fungus (Claviceps) a sweetish substance, known as honey dew. is se- 

 creted as the conidia ripen, and insects visiting the fungus for the honey dew scatter 

 the'spores. In the stinkhorn fungus (Phallus impudicus) the spore-bearing portion 

 deliquesces into a vile-smelling 

 mass that attracts flies, which 

 scatter the spores. Doubtless 

 many fungus spores also ad- 

 here to the slimy surface of 

 slugs and thereby are scattered. 

 Flies are among the most effi- 

 cient scatterers of spores, which 

 become attached to various 

 parts of the body, and occur 

 abundantly in the excreta ; the 

 spores or propagules of more 

 than fifty species of fungi and 

 bacteria have been found in 

 a single fly speck. 



Many fungus spores are able 

 to endure severe conditions. 

 For example, the spores of 

 Mucor and of Aspergillus have 

 been dried for two years, after 

 which they were exposed for 

 three weeks to a temperature 

 of 180 C., and for three days 

 to 253 C., without impair- 

 ing their capacity for germi- 

 nation. Desiccated bacteria 

 have been known to retain 

 their vitality for nearly a hun- FIGS. 1125-1127. Spores of the wheat rust (Puc- 

 dred years. It is concluded cima graminis): 1125, uredospores; 1126, young 

 from such experiments that all teleutospores; 1127, mature teleutospores; note that 

 vital activity mav be suspended the uredospores are one-celled, and the teleutospores 

 for long periods of time (p. QOO). tw - celled : h 'g hl y magnified; 1125, 1127 from 



... , . COULTER; 1126 from CHAMBERLAIN; (Part I). 



In part this endurance is due 



to unexplained features in the resting protoplasm, but there are also many instances 

 of protective structures or habits. In most ascomycetes the spores, though thin- 

 walled, are protected within the ascocarps (as in lichens and mildews, figs. 181, 182), 

 while in many hymenomycetes the thin-walled basidiospores are protected by the 

 piieus ; some of the so-called bracket fungi are hard and woody and capable of 

 enduring the winter. In the heteroecious rusts there are borne in spring and sum- 

 mer basidiospores (fig. 194), aecidiospores * (fig. 196), and uredospores (fig. 1125), 

 1 Sometimes aecidiospores and uredospores are regarded as sexually formed spores. 



