REED: SPECIALIZATION OF PARASITIC FUNGI 



383 



belonging to the various varieties of all the species of Triticum, with 

 the exception of certain ones, as those just noted, proved quite sus- 

 ceptible when they were tested under greenhouse conditions. Vavilov 

 suggests that the greenhouse conditions are much more favorable to 

 the development of the powdery mildew and thus more or less immune 

 races may be successfully attacked by the fungus. 



The writer (117, 118, 120) has carried on a very extensive series 

 of tests with the powdery mildew of the wheat. One hundred and 

 sixty-one varieties belonging to the eight recognized types or species 

 of Triticum have been tested under greenhouse conditions, many tests 

 having been made with nearly all of these. The results are summarized 

 in the following table: 



Varieties of Species or Types of Triticum in Relation to the Wheat 



Mildew 



It is thus seen that the great majority of the varieties are highly 

 susceptible to the wheat mildew. It may be specially noted that T. 

 dicoccoides Kcke. the wild wheat of Palestine, proved to be quite 

 susceptible. The distinctly resistant varieties included T. dicoccum 

 var. Khapli, Riissian emmer and Spring emmer and T. vidgare var. 

 caesium and pyrothrix. 



Various other species of Triticum have also been tested, T. bicorne 

 Forsk and T. caudatum Gren. & Godr. proving to be highly susceptible 

 and T. triaristatiim Gren. & Godr. and T. triuncinale Rasp, proving to 

 be resistant. 



The writer (119, 120) has also found that the powdery mildew of 



8 Summary includes Triticum Cienfuegos Lagh., T. dicoccoides Kcke., T. Frey- 

 cenetii Host., T. Meyeri, T. Tumonia Schrad. and T. durum Desf. var. plenissimum^ 



'• Summary includes T. abyssinicum Steud. and 7". dicoccum Schrank var. campy- 

 lodon. 



■ * Summary includes T. Thaoudar Reut. and T. dicoccum Schrank var. cladurum. 



' Summary includes T. durum Desf. var. africanum and Triticum species indet. 

 var. Tibetan. 



