98 James G. Horsfall 



Symptomatology 



Probably the most characteristic symptom is circular to elliptical, 

 small, purple-brown spots, with brown to gray centers, dispersed over the 

 leaf surface. These spots seem to be more in evidence when the disease 

 occurs on mature tissues, for they are most frequently conspicuous late 

 in the season. These spots on timothy leaves may be seen in figure 23. 

 These leaves show chiefly, however, the long aniline to sulphine yellow 

 streaks (Ridgway, 1912) which result from elongation of the spots parallel 

 to the midrib. An incipient stage of the latter type of spotting is shown 

 at A in figure 23. 



The disease appears to be slightly different early in the season on 

 orchard grass as the following notes on symptoms, taken in May, 1928, 

 indicate: The spots occur on leaf sheaths and blades where they tend to 

 congregate on the midrib, resulting in a cracking of the tissues at that 

 point. They appear at first as small elongate, hydrotic areas, but they 

 enlarge rapidly, soon becoming one to two centimeters long or even longer. 

 The hydrotic center early in the morning when the dew is on is deep 

 olive gray (Ridgway, 1912), but upon drying it becomes deep dull gray. 

 This is surrounded by a band of pecan brown, and this in turn by a narrow 

 strip of maize yellow. The spots occurring toward the proximal end of 

 the leaf cause it to turn yellow over the entire length. 



All the symptoms described were noted on the spots that bore the 

 minute black conidial stromata. These are arranged in rows in the 

 center of the spots parallel to the veins of the leaf. 



Etiology 



Name, history, and classification of the pathogene. Fuckel in 1863 

 described the causal organism as Scolecotrichum graminis in Fungi Rhenani 

 Exsiccati (1863 : 134) . Subsequently many species of Scolecotrichum as well 

 as varieties of S. graminis were described on grasses. Recently, however, 

 von Hohnel (1924:6-7) has shown that the genus Scolecotrichum prob- 

 ably is invalid. He places this fungus in Passalora graminis (Fckl.) 

 Hohn. and includes S. compressa Allescher (Hedwigia 35 2 :34. 1896) and 

 S. graminis (Fckl.) var. nana Sacc. (Annales Mycologia 3:515. 1905.) 

 as synonyms, saying that they pertain to the young condition of the 

 fungus. 



Von Hohnel seems to have overlooked Cercospora graminicpla (Tracy 

 and Earle, 1895 a: 179) in his disposition of the fungus. Type material 

 of this fungus, which was kindly lent to the writer by Dr. Charles Chupp, 

 was compared with various American collections of S. graminis and speci- 

 mens in European exsiccati for which the writer is indebted to Dr. John 

 A. Stevenson of the Office of Mycology, Bureau of Plant Industry, Wash- 

 ington, D. C. The identity of the two fungi is obvious. The genus 



