204 AGRICULTURAL EXPERIMENT STATION. [Jan. 



SPOEES, and well illustrated by the spores which compose 

 the black streaks which follow the red rust on the stalks of 

 grain, and are known as " black rust." 



A few fungi form peculiar bodies, which serve the purpose 

 of resting spores, although they are of a very different 

 nature. These are dark-colored masses of closely compacted 

 mycelium, which can retain their vitality for a long time 

 under circumstances unfavorable to growth, and finally, 

 wdien favorable conditions recur, produce spore-bearing 

 structures and spores. These special resting mycelia are 

 known as sclerotia, and are well illustrated by the ergot of 

 grain, often known as " spurred rye." 



A given species of fungus may produce, not merely one 

 but two or several forms of spores and spore-bearing struct- 

 ures. These various forms may be produced at the same 

 time or at nearlj^the same time, on the same mycelium ; and, 

 when this is the case, their connection and relations to each 

 other are comparatively easy to make out. For instance, 

 the streaks of rust on the culms of grain may often l)e found, 

 at the proper season, with both red and black spores arising 

 from the same mycelium, showing that the red and black 

 rusts are onlj' different spore-forms of the same fungus. But 

 so simple a condition as this is the exceptional rather than the 

 usual one. In very many fungi, the spores produced on one 

 mycelium develop other mycelia essentially indistinguishable 

 from the first, on which spores very unlike the first are 

 formed ; and these may, in their turn, give rise to a mycelium 

 bearing spores like the first. For example, the mycelium 

 developed next spring from the spores of many black rusts 

 of the present season will produce, not new rust spores, but 

 chains of wholly different spores, arranged in the form of 

 tiny circular masses, each surrounded by a fringed or ragged 

 border. From this characteristic structure, and the fact 

 that they usually grow in close groups, these peculiar forms 

 of fructification have received their name of cluster cups. 

 On the mycelium arising from their spores are developed 

 again rust spores like those which gave rise to the cluster- 

 cup mycelium. Or again, the same mycelium may produce 

 two or more forms of spores at quite difierent times, so that 

 their connection is not directly traceable except by keeping 



