gI 
When in 1864 De Bary announced in his now classical paper 
that the A*cidium on barberry was but a stage in the life cycle of 
Puccinia graminis and in 1865 that Aecidium asperifoli and 
Aec. rhamni were similarly related to Puccinia rubigo-vera and 
coronata it was thought that the life-history of the cereal rusts 
was settled and done with and that the number of species of the 
Uredineze was wonderfully reduced. One or two carping 
critics would however persist in pointing out that the whole 
matter was not cleared up quite so completely ,that for instance 
there were certain districts in England from which the barberry 
was absent but where from time to time the wheat crop was 
seriously injured, nay further there were countries, in some of 
our colonies especially, in which no barberry grew but in which 
more damage was done to the wheat crop than was even the 
case in those parts of Europe, where the shrub is comparatively 
common. 
We now know of course both groups of facts are perfectly 
true, and although we are unable completely to explain every 
detail of either, it only remains for us to work on steadily 
accumulating information, piling together observations, and if 
we only go on long enough we shall in due time understand the 
whole question. We got but little light on this wheat mildew 
problem until Eriksson in 1894 showed us that the so-called 
si ee LH? Tepresents a number of biological species : 
n have their ecidiospores on the barberry but their 
led species, 
