Morphology. 35 



form from the spores or goniclia of tlie otlter^ or to 



show that the two phases are in organic continuity. 



Parasitism between fungi has led to mistakes in this 



connection. 



In the Uredinese, a group of fungi parasitic on living 



plants^ pleomorphism was first demonstrated by De 



Bary, who showed that three independent forms, 



hitherto considered as distinct species, were in reality 



only phases in the life cycle of one species. The first 



form, called Ureclo linearis, appears on the leaves of 



wheat during the summer in the form of minute red 



streaks formed by closely compacted, one-celled, 



brown, minutely warted spores ; daring the autumn 



the same mycelium that produced the Uredo during 



the early part of the year gives origin to blackish 



streaks consisting of spores that are quite distinct 



from the Uredo spores in being smooth, two-celled 



and darker in colour. This received the name of 



Puccinia graminis. The Puccini a spores, after having 



remained during the winter in a passive state, 



germinate and produce small secondary spores, these 



must find their way on to the surface of a barberry 



leaf, where they germinate, enter the tissues of the 



leaf, and within a short period of time give origin to 



a minute fungus that was called ^ciclium herheridis, 



and popularly known as cluster -cicps. Finally, when 



the ^cidium spores are placed on the leaves of young 



wheat plants, the Uredo form is again produced. 



Now, in the above example of pleomorphism, it can be 



proved beyond doubt, and with comparative ease, the 



three forms enumerated are phases belonging to one 



species, because the spores of the Uredo stage can be 



D 2 



