254 EXPERIMENTAL FARMS 



4-5 EDWARD VIl., A. 1905 



fuse production of another kind of spores, brownish black in colour. These are the 

 teleutospores, and are the means of carrying the parasite over the winter. These blaok 

 winter-spores frequently appear in this species in the same spots on the stem, where 

 the red-rust stage was earlier in the season, but do not germinate until the following 

 spring. 



RUST AKD THE BARBERRY. 



In addition to these two forms of the Black Stem Eust, there is another stage 

 which has been the subject of much controversy. This comes from the spores of the 

 first generation in spring falling upon the leaves of some species of barberry, where 

 they give rise to a curious fungus, known as Barberry Cluster-cup. After a time this 

 matures and pours out enormous numbers of spores which are carried in all directions 

 by the air and fall upon grain plants, where they give rise to Red Rust. Strange to 

 say, this remarkable fact in the life history of rust was discovered very many years 

 ago, and laws looking to the extermination of t]ie barberry plant date back to 1660, 

 when an Act having this object in view was passed in France. 



It is not, however, absolutely necessary for Rust to have its first stage on the bar- 

 berry, although experiments have shown beyond doubt that it does sometimes occur on 

 that plant. The theory has been advanced that growing in this way in one of its 

 stages on the barberry gives the parasite greater vigour; but it is beyond question 

 that the Black Stem Rust can continue to grow in localities where no barberries are 

 grown, and it is also known to occur in specialized forms on many of the wild prairie 

 grasses. Among the samples of grasses sent to me from Manitoba with the rusted wheat, 

 were specimens of the Skunk- tail grass, or Squirrel-tail (Hordeum juhatum), which 

 bore well developed pustules of Black Stem Rust, similar to those which occur on 

 wheat and cultivated barley. The Skunk-tail grass is a very bad weed of the West, 

 and certainly increases in hay lands, owing to a habit farmers have of leaving this 

 grass uncut when mowiug, so that it ripens and distributes its seeds. If it were cut 

 down at the same time as hay, the unripe seeds would soon dry up, or might be easily 

 burnt after the hay was carried. Mr. Mark A. Carleton, Cerealist of the United States 

 Bureau of Plant Industry, who has made extensive investigations of rusts, writes as 

 follows : — 



' It is positive now from experiments made by this department that the Rust of 

 'Hordeum juhatum will easily transfer to wheat and barley, and therefore it would 

 decrease the chance of infection of a wheat field, if this grass could be kept out of the 

 wheat, or if the wheat were sown away from its influence.' 



REMEDIES. 



Little can be done as a remedy against rusts; but, as the parasite passes the 

 winter on the old straw, land left for seeding on stubble should be burnt over care- 

 fully before seeding, and the ploughing down of stubbles for summer-fallow should be 

 done as early as possible in the season, so as to prevent as much as may be the dis- 

 tribution of the first generation of spores. Rusted straw fed to cattle is said to dis- 

 tribute the fungus in grain crops from the spores being carried through with the 

 manure. Fresh manure, therefore, should not be used in fields where grain is to be 

 grown. The investigations which have been carried on in Australia, have run largely 

 towards the discovery of varieties of grain which may be more or less exempt from the 

 attacks of rust. Although probably no variety has yet been found entirely free from 

 these parasites, still much has been learned as to the comparative immunity of some 

 kinds, and Mr. Carleton points out tlxit the investigations are said incidentally to have 

 resulted in Australia now having varieties of wheat which are vigorous, true to name, 

 and of exceptional quality for the particular region in which they are grown. 



