ORANGE LEAF RUST OF WHEAT. 21 



tlie orange leaf rust of wheat in this country: Triticnm ridgarc, T. com- 

 j)actum, T. turf/hbini, T. durum, T.spelta, T.dicocciiin, and T. polonknm. 

 These are all cultivated varieties, but varietii^s of the three last named 

 have been grown so far in this country only in an experimental way. 



Occurrence and dutribution.— It is a well-established fact that the 

 orange leaf rust of wheat is the most common and widely distributed 

 of all the cereal rusts in the United States, and is especially the most 

 constant in occurrence from year to year. The stem rust and the crown 

 rust do not occur on cereals in certain years and certain localities. 

 The orange leaf rust of rye, although occurring wherever rye is growu, 

 is still not common, because rye is not grown generally. Maize rust 

 usually occurs wherever corn is grown, but is seldom abundant; but the 

 orange leaf rust of wheat is not only never absent from the wheat field, 

 being there the year through, but is sometimes abundant even iii dry 

 seasons. There is still so much uncertainty as to the identification of 

 species that as yet it can not be definitely said whether this rust is the 

 most common in foreign countries also, but the probabilities are that 

 it is, at least in all except the countries of northern Europe. In Aus- 

 tralia and India there is no doubt of its being the most common, pro- 

 vided that our leaf rust and the one iu these countries are eciuivalent, 

 which is almost certain. Barclay (5, Vol. XXVIII, p. 257; Vol. XXX, 

 p. -lO) is quite emphatic as to its being the most common in India.' In 

 Sweden the conditions seem to be exceptional. Tlie most common, as 

 well as the most injurious rust in that country, according to Eriksson 

 (31, pp. 208, 209,331), is P. ghmarum, while P. dlspersa is rather insig- 

 nificant both as to its occurrence and tlie injury it causes.^ 



Wintering of the uredo.—^o much has already been written concerning 

 the wintering of the uredo and the ability of the fungus to readily pass 

 the Aviuter in the uredo stage is so well established for this country that 

 there is little further to add. However, it may perhaps be well to state 

 that the conclusions of Bolley (7, pp. 13-15) and of Hitchcock and the 

 writer (39, pp. 1, 2) have been confirmed and reconfirmed by the writer 

 both in Kansas and Maryland. In the Southern States the leaf rusts 

 of both wheat and rye not only live, but grow all winter. It is now 

 conclusively proved that in latitudes below 40'=^ in this country the leaf 

 rust of wheat is able to pass a perpetual existence in the uredo stage 

 on wheat alone^ without the intervention of any other stage. This is 

 evidently a matter of much economic importance, for if this method is 

 not only possible, but should turn out to be the only one, it is easy to 



' Through the kindness of the Government officials of India the writer received 

 specimens of rusted wheat straw from that country. The rust most abundant on 

 the specimens seems to be morphologically enough like our own Fiiccinia riiUfjo-vera 

 to be called the same, specimens showing the second and third stages of this rust 

 being present. However, P. (jramiuis was also found in considerable amount. 



2 At the writer's request Dr. Eriksson kindly sent him specimens of both P. ghma- 

 rum and /'. dispersa. An examination of these specimens showed that with the 

 exception of a slight difference in color there is a very close resemblance morpho- 

 logically lietweeen the latter and our F.rubiijo-vera. 



