224 



seems now riot to be the least doubt but that it can pass the winter in the 

 uredinial stage ; in fact, McAlpine 24 claims that in Australia the secia 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 23 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 aecium. 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 26 and by Johnson 27 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. 28 Carleton, 29 and Christman. 60 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, 31 and by Christman, 32 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 aecia. Oarleton, 33 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 

 I'iKirum. is found over most of North America. Only in the far west, 

 however, does it produce teliospores, and so only in this region can it have 



"Rusts of Australia 66-67. 1906. 



- 5 Bot. Gaz. 52:169-192. 1911. Phytopathology 1:150-154. 1911. 



"Phytopathology 4:337-338. 1914. 



"Bur. Plant Industry Bull. 224:12-13. 1911. 



^Microscopical Journal Mch., 1890: 59-60. 



"Div. Veg. Phys. and Path. Bull. 16:21. 1899. 



3"Trans. Wis. Acad. Sci. 15:98-107. 1905. 



"Bur. Plant Ind. Bull. 216:56. 1911. 



SI Trans. Wis. Acad. Sci. 15 l :106-107. 1905. 



"Bur. Plant Ind. Bull. 63:20. 1904. 



