Ward. — Recent Researches on the Parasitism of Fungi. 47 
and Dietel ( 55 , p. 43) confirmed Plowright’s results ; though Klebahn found 
it infect both Arum and Allium , but not Convallaria , Polygonatum , Majan- 
tkiemum , Orchis , or Lister a. However, teleutospores obtained from Arum 
the following year refused to infect any but Arum. Now the question 
before us is, Are the forms now known as P. Allii-Phalaridis , Kleb., P. 
Ari-Phalaridis , Plowr., P. Convallariae-Phalaridis , Sopp., P. Smilacearum- 
Phalaridis , Kleb., P. P arid i -Digraph idis^ Plowr., P. Or chide arum- Phala- 
ridis , Kleb., &c., all with their puccinia-form on Digraphis and their 
aecidium-form on the host referred to, to be accepted as species ? 
To me it is impossible. Until morphological characters can be found 
which separate it satisfactorily into specific forms, the Puccinia on Digraphis 
must be regarded as one and the same morphological species. But it does 
appear as if this species was adapting itself more and more closely to 
different alternate hosts, on which to develop its aecidia. Whether 
this adaptation will ultimately result in the breaking up of the various 
races into species is another question. 
There are several possibilities, suggested by experiment but by no 
means as yet decided, to be kept in view in future investigations. 
It is, for instance, quite possible that these adaptations are local, in the 
geographical sense ; that a Puccinia which in one geographical area is 
in the habit of infecting one alternate host, in another, where that host 
is rare or absent, has to adapt itself to another. Klebahn’s results with 
P. Conopodii-Bistortae and P. Angelicae-Bistortae (P. Cari-Bistortae ) may 
well be quoted in support of such a view. 
Another possibility, in support of which Klebahn’s results with 
P. Convallariae-Digraphidis and P. Smilacearum-Digraphidis might be 
quoted, is that the age of the plant, or the complex of events we term 
weather, may decide which of a number of potential host-plants shall 
be chiefly infected during a particular season. 
Yet again, we may find that different conditions of culture of the 
teleutospores may impress on them differences in infective capacity for 
different alternate hosts, as Klebahn ( 98 , p. 152) has suggested for certain 
cases. Whichever view comes to be most accepted in the future, how- 
ever, it seems impossible to escape from the conclusion that specific 
susceptibility on the part of the host will also have to be taken into account. 
So far our speculations have concerned the adaptation of the parasite 
in the alternating phases of its existence — e. g. of the Puccinia to a second 
host on which it can form its aecidium. 
But the peculiarity of specialized parasitism, in the more modem sense 
of the phrase, and due chiefly to Eriksson’s work, is that each phase of the 
Fungus- — e. g. the uredo-form — also adapts itself to various species, races, 
or varieties, and I now propose to inquire into the meaning of this. 
Eriksson’s experiments resulted in not only an extension of the above 
