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1898 | RESEARCH INTO GRAIN RUST 27 
1. The kinds of fungus which produce rust in cereals are at least 
ten in number (partly species, partly specialized forms of species), and 
the spread of the disease from one kind of cereal or grass to another is 
thereby considerably restricted. 
In order to illustrate the situation of the grain rusts in this 
regard, I would call attention to the accompanying table, in 
which can be seen what the former situation was, that is to say, 
in 1890 when this investigation began, and what it is now in the 
summer of 1897. 
At the first glance this table shows how different the position 
is now from what it was formerly. Then we supposed that 
three species of rust were found on our cereals; one of them 
called Puccinia graminis occurred on all the four cereals, another 
P. rubigo-vera (P. straminis) on rye and wheat, and a third P. 
coronata on oats, to which finally a fourth form, P. semplex on 
barley, was added, ordinarily considered to be only a variety of 
P. rubigo-vera. We also thought that all the kinds of Graminee 
that bore a certain species of rust (P. graminis is observed on a 
hundred species of Graminez in Sweden) were able to infect 
one another. 
How different our apprehension must now be! It appears 
that if we stop with the four cereals we have to count in Sweden 
not less than ten different forms of rust, and I have cause to 
suspect that on the continent of Europe one or two other forms. 
are to be found. These ten forms are distributed among at least 
five species in such a way that there occurs 
(1) One form of black rust on rye and barley, 
(2) One form of black rust on oats, 
(3) One form of black rust on wheat, 
(4) One form of yellow rust on wheat, 
(5) One form of yellow rust on barley, 
(6) One form of yellow rust on rye, 
{7) One form of brown rust on rye, 
(8) One form of brown rust on wheat, 
(9) One form of dwarf rust on barley, and 
{10) One form of crown rust on oats. 
