14 Ward, — Recent Researches on the Parasitism of Fungi, 
Lagerheim (102) found the uredo of P. Poarum just after the melting 
of the snow about it ; and Dietel (56) describes two kinds of uredospores 
in P. vexans , the thicker walled of which he regards as resisting the winter. 
I myself found germinable uredospores of P, dispersa on Brornes 
during every month throughout the year 1 901-2, even in February and 
March, the least favourable of times. 
Plowright in 1882 also found uredospores on Agtopyrum repens at 
the end of December and in March, and says that those of P, ‘ Rubigo-vera ’ 
can be got all the year round. 
Hitchcock and Carleton (84) found uredo on Wheat all through 
January, February, and March, and Carleton says that P . ‘ Rubigo-vera * 
Tritici lives all the year round in the uredo-state as we pass from the 
Southern to the Northern States ; while Bolley confirms this, and asserts, 
further, that even in the Northern States he finds the germination- 
capacity preserved through the winter. 
Even Eriksson (62, pp. 153-4) admits Nielsen’s statement that uredo 
withstands the winter on green leaves ; and other cases given by Kuhn (110), 
Blomeyer (34), Rostrup (142), McAlpine and Cobb (40), go to swell the 
evidence that we cannot afford to overlook such facts as the above in 
discussing the question of the period of infection, or of the limits of 
germination-capacity of these spores. 
Specialized Parasitism. 
Before proceeding to consider the details of infection and consequent 
phenomena, it is necessary to break the thread of our story, as it were, 
in order to render clear a subject which becomes more and more involved 
in the cycle of phenomena yet to be described. After the period of 
research in which investigators had been concerned chiefly with the hunt 
after new cases of heteroecism, and with the unravelling of the species 
of Uredineae from the threatening chaos to which their rapidly increasing 
numbers was leading, the next step of fundamental importance was the 
discovery of specialized parasitism. 
Before going into this question I may remind you that the matter has 
a history behind it. The older observers, e. g. Persoon, of course named 
each Fungus on a different host as a distinct species, or even genus, as 
the words Aecidium , Peridermium , Roestelia ; Pnccinia , Coleosporium , 
Gymnosporangium ; Uredo , Uromyces , &c., sufficiently attest. 
Then came the controversy regarding polymorphism, and the Tulasnes 
and De Bary especially did yeoman’s service in proving that even heteroe- 
cious forms passed through such stages as Uredo , Puccinia , and Aecidium. 
The next stage was the proof that species like Puccinia graminis and 
Peridermium Pini , in the old sense, were really composite forms ; and that 
the aecidia of the different cereal forms were developed on plants other 
