154 TEXT-BOOK OF FUNGI 



forms is permanent under various conditions, a subject 

 lately investigated by Salmon, in a series of experiments 

 which gave the following results. The host-plant chosen 

 was barley, the fungus being the biologic form of E. 

 graminis on wheat. It had previously been ascertained 

 by repeated experiments that this biologic form on wheat 

 is not able, under ordinary conditions, to infect barley. In 

 these experiments plants of barley were abundantly inocu- 

 lated with both conidia and ascospores, while others were 

 allowed to stand for several months among virulently 

 infected wheat plants, where they were constantly exposed 

 to infection ; in every case the barley plants remained 

 persistently immune. By using certain cultural methods, 

 however, Salmon succeeded in rendering barley susceptible 

 to infection by the biologic form on wheat. The barley 

 before being inoculated was treated as follows : The leaves 

 were either (i) mechanically injured locally in one of the 

 following ways a small portion of leaf-tissue was cut out, 

 or pressure was applied so as to bruise a group of leaf-cells, 

 or the surface of the leaf was 'touched at one spot with the 

 red-hot point of a knife, or the leaf was injured by allowing 

 slugs to eat out large pieces ; or (2) the whole leaf was 

 exposed for a short time to the action of ether or chloro- 

 form, or immersed in a mixture of alcohol and water, or 

 heated up to 50 C. in water. The treated barley leaves 

 were then inoculated with ascospores or conidia taken 

 from the biologic form on wheat, and proved susceptible. 

 In the case of the mechanically injured leaves only the 

 cells immediately adjoining the place of injury became 

 infected ; in the cases where an anaesthetic or heat was 

 employed, infection resulted here and there over the 

 whole surface of the leaf. In both cases patches of 



