A Study of Meadow-Crop Diseases in New York 89 



by copious infections, but when only one or two small infections occur 

 scattered over the leaf, little or no discoloration appears adjacent to them. 

 Sometimes there is a narrow zone of yellow surrounding each pustule. 

 Barker and Hayes (1924:367) note that " very sharp hypersensitive areas 

 do not appear in timothy. Resistant plants give small pustules which 

 are not confluent. Marked chlorosis is usually, but not always, associated 

 with resistance." 



Timothy rust is most noticeably evident on leaves and culms in the 

 urediniospore stage as yellow-brown, characteristically elongated pustules 

 protruding through the epidermis which is visible with a hand lens as a 

 whitish partially sloughed off scale. The oblong linear sori may approach 

 5 millimeters in length. In some instances they are confluent. The 

 uredinial sori on timothy culms are shown in figure 20. Note the scurfy 

 appearance due to the bits of epidermis which have been pushed aside by 

 the developing sori. 



Etiology 



Name, history, and classification of the pathogene. Even after more than 

 twenty-five years the question that Eriksson asked in 1902 seems to 

 persist, " 1st der Timotheengrasrost eine selbstandige Rostart oder nicht?" 

 In 1894 Eriksson and Henning (1894:140) described a new species, 

 Puccinia phlei-pratensis, on timothy, differentiating it on the basis of the 

 lack of an aecial stage on Berberis. In 1902 Eriksson asked the question 

 just quoted and maintained that it should be a separate species. He 

 thinks (1902:198) that Puccinia phlei-pratensis may have arisen originally 

 from Puccinia graminis and " that it has differentiated gradually over a 

 long period of time into a distinct species, in so far that it has lost its 

 aecium-producing capacity, but that it has retained its inner nature so 

 that it can return weakly to oats and rye." Klebahn (1904:235), Svdow 

 and Sydow (1904:784), and Evans (1907:447) likewise retain Eriksson's 

 name. 



Kern (1909) maintains that Eriksson's one successful inoculation of 

 barberry is worth mo e than all the negative results since obtained, so 

 that he advocates calling the fungus a physiological form of Puccinia 

 poculiformis (graminis). A year later (1910:418), however, he retracts 

 somewhat and says, " Rather than calling it a race, physiological species 

 or form species, it might be better to consider it a variety or subspecies 

 since it does, as previously pointed out, possess some slight morphological 

 differences from the typical form, particularly in the small aecial cups 

 and the more delicate uredinial mycelium." Johnson (1911), Pammel 

 and King (1912), and Mercer (1914) use the name Puccinia phlei-pratensis. 

 Stakman and Jensen (1915) avoid naming the fungus in their paper report- 

 ing inoculation experiments, but Stakman and Piemeisel (1916) call it 



