REPRODUCTION AND DISPERSAL 



813 



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 Ascoholus 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 tor 

 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 tor nearly a hun- 

 dred years. It is concluded 

 from such experiments that all 

 vital activity may be suspended 

 for long periods of time (p. 909). 

 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 

 pileus ; 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 ig4), aecidiospores ' (fig. 196), and uredospores (fig 1125), 

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



Figs. 1125-1127. — Spores of the wheat rust (Puc- 

 cinia gmminis): 1125, uredospores; 1126, young 

 teleutospores ; 1127, mature teleutospores ; note that 

 the uredospores are one-celled, and the teleutospores 

 two-celled; highly magni&ed; 1125, 1127 from 

 Coulter; 1126 from Chamberlain; (Part I). 



