RUSTS 283 



land. There is a village in Norfolk that long went by the 

 name of " Mildew RoUesby," on account of the mildewed 

 grain caused, it was believed, by the abundance of bar- 

 berry bushes in the neighborhood. These were cut down 

 and mildew at once disappeared. Repeated instances of 

 the kind led a few men of science to suspect that the pop- 

 ular behef might be something more than a mere supersti- 

 tion, after all. Experiments were made which showed that 

 grain planted in the vicinity of a barberry bush infected 

 with aecidia developed rust immediately after the secidia 

 spores matured, and that rust was most abundant in the 

 direction in which the wind carried the spores. Further 

 experiment showed that aecidia spores would not germinate 

 directly on barberry ; in other words, aecidia would not re- 

 produce aecidia directly, but only after passing through one 

 or more intermediate stages, and thus it was proved beyond 

 a doubt that these fungi are not independent plants, but 

 merely a phase in the life history of the Puccinia. 



405. The Life Cycle. — Taking the first phase of the 

 season as our starting point, the life cycle of the wheat 

 rust consists of three stages carried on by four different 

 kinds of spores: (i) The non-parasitic stage, which origi- 

 nates from teleutospores, and produces sporidia ; (2) The 

 aecidium phase, which arises from the sporidia, is parasitic 

 on barberry, and produces spores that germinate on grain ; 

 (3) The uredo-teleuto phase, parasitic on grain. The first, or 

 sporidia stage, which is too small to be discoverable except 

 by the microscope, escapes the notice of the ordinary ob- 

 server, and the third, producing two kinds of spores, uredo 

 and teleuto, has the appearance of being two separate 

 stages, so that to one unacquainted with the facts, the life 

 cycle would seem to consist of a red rust or uredo stage, a 

 black rust, or teleuto stage, and an ascidium stage. The 

 last is often omitted. In many cases, as in our own south- 

 ern States, where there are no barberries to act as hosts, 

 the sporidia germinate directly upon young wheat, without 

 passing through the cluster cup stage, and the orange leaf 



