224 
seems now not to be the least doubt but that it can pass the winter in the 
uredinial stage; in fact, McAlpine* claims that in Australia the cia of 
the rust do not exist and that the rust will not infect the barberry. As to 
the exact method of wintering there is some difference of opinion. The 
contention by Pritchard” that teliospores or mycelium in the seed grain 
have something to do with its propagation in wheat is different from all 
the others in the suggestiveness that a sexual process may be involved even 
in the absence of the cium. All other theories which have been advanced 
assume a strictly asexual propagation, and probably Pritchard’s theory 
does not really assume otherwise either. Perhaps the most famous theory 
is Henning’s now discredited mycoplasm theory. The real means by which 
the rust passes the winter is probably mycelium in the leaves of the host 
plant. The presence of this mycelium during the winter months has been 
shown by Hungerford” and by Johnson” in the leaves of timothy. 
That the leaf rust of wheat is carried through the winter in*the same 
way is shown by the findings of Bolley,* Carleton,” and Christman.” This 
method of carrying the fungus over accounts satisfactorily for the heavy 
early infection, followed by a period of little or no infection, which is in 
turn followed by the epidemic proper. The old leaves, which are infected 
from the autumn, carry the first epidemic and then die, the mycelium, of 
course, dying with them. In the meantime the new leaves have been in- 
fected; and in about four weeks, which as has been shown by Freeman 
and Johnson,” and by Christman,” is the approximate incubation period for 
that time of year, the uredinial stage breaks out freely on them. 
Aside from the work with the grain rusts, not much has been done in 
the way of determining the method of passing the winter by rusts in 
regions remote from their «cia. Carleton,® however, states that Puccinia 
montanensis on Elymus winters in the uredinial stage, and calls attention 
to the situation with regard to the bluegrass rust. This rust, Puccinia 
Poarum, is found over most of North America. Only in the far west, 
however, does it produce teliospores, and so oniy in this region can it have 
“Rusts of Australia 66-67. 1906. 
*Bot. Gaz. 52:169-192. 1911. Phytopathology 1:150-154. 1911. 
Phytopathology 4:337-338. 1914. 
27Bur. Plant Industry Bull. 224:12-13. 1911. 
2sMicroscopical Journal Mch., 1890: 59-60. 
Div. Veg. Phys. and Path. Bull. 16:21. 1899. 
wTrans. Wis. Acad. Sci. 15:98-107. 1905. 
“Bur. Plant Ind. Bull. 216:56. 1911. 
Trans. Wis. Acad. Sci. 151:106-107. 1905. 
Bur. Plant Ind. Bull. 63:20. 1904. 
