42 CEREAL RUSTS OF THE UNITED STATES. 



Certain instances seem to show that occasionally, when this rust, 

 appears suddenly or unusually early in dry seasons, it is capable of 

 doing some injury indirectly, either by preventing the leaves (its chief 

 point of attack) from elaborating sufficient food material for the plant, 

 or by causing too great transpiration through injury of the leaves, or 

 in both ways. Galloway (35, pp. 445-452), in his article on leaf casting 

 of Finns rirginiana, records important exi)eriments, which show the 

 increase of transpiration in rust-injured leaves of the pine. In the 

 experiments at Manhattan, Kans., in 1897, the grain of many experi- 

 mental varieties of wheat was considerably injured, and seemingly, in 

 part, at least, by this rust. Just after the appearance of the rust in 

 great abundance a dry period set in and continued until harvest. But 

 even in this case P. graminis was also present in considerable quantity, 

 and may really have caused the injury. Eriksson (27, pp. 245-248) 

 claims that the first instance of any injurious occurrence of P. dispersa 

 that he observed in Sweden was in the season of 189G, the first twenty 

 days of June of this year being drier and hotter than any correspond- 

 ing period in seven years. 



Certain phenomena observed during the experiments at Garrett Park 

 led the writer to think that in very wet seasons this rust may be actu- 

 ally of some benefit to the grain by preventing too much growth of the 

 vegetative parts of the plant at the expense of the reproductive por- 

 tions. Though many varieties jiroduced shriveled grain in these ex- 

 periments, those most severely affected with rust produced good grain. 

 Little (47, p. 640), in his discussion of wheat "mildew" in England, 

 also refers to this. He notes that "in the Feu districts, which suffer 

 most from mildew, the prevalence of this spring rust ( Uredo ruhigo- 

 vera) is believed to be rather beneficial than otherwise, as it reduces 

 the excessive luxuriance, which is usually the result of a mild wiuter, 

 and which is popularly supposed to make the wheat crop more liable 

 to mildew." 



OKANGE LEAF RUST OF RYE. 



{Puccinia ruhigo-rera secalis). 



Physiological relations. — Although this rust strongly resembles the 

 orange leaf rust of wheat, inoculation experiments have shown that 

 there is not only no i)hysiological connection between them, but that 

 the orange leaf rust of rye can not, so far as the writer has yet deter- 

 mined, be transferred by inoculation to any grass, wild or cultivated, 

 excej^t SecaU montanum. Experiments with the uredo of this rust were 

 begun in the spring of 1896 with material which was kindly sent to the 

 writer by Prof. F. S. Earle, of the Alabama Agricultural Experiment 

 Station. 



