DT-MORPHISM. 33 



CHAPTER III. 



DI-MORPHISM. 



BEFORE entering farther and more fully upon 

 the subject of this volume,, it may be advisable 

 to attempt an explanation of a phenomenon of no 

 uncommon occurrence in many groups of Fungi, 

 and which is termed di-morphism. 



In the Uredines, or uredo-like fungi, as well as 

 other of the Coniomycetes (in which the spores are 

 the principal feature), the same fungus appears 

 under two or more distinct forms, not necessarily 

 mere differences of age, but so distinct that they 

 have been regarded (and some are so still) as 

 different species belonging to different genera, 

 often far removed from each other, and bearing 

 different names. One plant, for instance, sprinkled 

 over the under surface of a rose-leaf, like turmeric 

 powder, has its mycelium, or root-like threads, 

 penetrating the tissue, whilst bearing above its 

 spherical golden-coloured spores. Its vegetative 

 system is complete, and, apparently, its reproduc- 

 tive also ; hence it seems to claim recognition as a 

 perfect plant, and under the name of Uredo Rosce 

 was so recognized, until microscopical investigation 

 determined otherwise. Thus it has been discovered 

 that certain dark brown spots which appear later 



D 



