76 James G. Horsfall 



hydrotic at first but later dry and show the dark zones and the dark 

 margins evident in the photograph. The papery character of the central 

 portion of the spots on sweet-clover leaves is shown in figure 17. 



The minute dark pimples, the pycnidia, are to be seen prominently in 

 the light-colored centers of the spots. These are characteristic signs of 

 the disease. 



The author experienced difficulty at first in identifying the causal fungus. 

 It has been classified under various names according to the age of the spores 

 and the suscept involved. The writer at first identified it on red, alsike, 

 and white clovers as Phyllosticta trijolii; on yellow trefoil as Phyllosticta sp.; 

 on red clover as Septoria compta or Septoria trijolii; on alfalfa as Ascochyta 

 imperfecta, A. meclicaginis, or Stagonospora carpathica; on sweet clover as 

 Ascochyta meliloti, A. caulicola, or Stagonospora meliloti. Single spore 

 cultures from the Phyllosticta on alsike and white clovers, the Ascochyta 

 on alfalfa, and the Stagonospora from sweet clover, were identical in 

 appearance under the same cultural conditions. The color of the thalli, 

 the yellow color imparted to the medium (oat agar), and the size, shape, 

 and septation of the spores were the same. The fungi agree in every 

 respect with Stagonospora meliloti rom sweet clover. At the completion 

 of this experiment the writer realized the then very obvious correspondence 

 of the symptomatology on the various suscepts and concluded that the 

 Sphaeroidaceous fungi under consideration on the legumes are probably 

 identical. Subsequently in perusing the literature on Sphaeru ina trijolii, 

 a paper by Petrak (1919) was discovered in which he has combined all these 

 fungi under the name Stagonospora meliloti (Lasch) Petrak. He lists the 

 following names as synonyms: Sphaeria meliloti Lasch, Septoria meclicaginis 

 Desm. et Rob., Septoria compta Sacc, Septoria meliloti Sacc, Phleospora 

 trijolii Cav., Stagonospora carpathica Baumler, Stagonospora trijolii Fautr., 

 Stagonospora trijolii Ell. & Ev., Stagonospora dearnessii Sacc, Stagonospora 

 medicaginis v. Hoh., Stagonospora compta Died., and Ascochyta caulicola 

 Laub. This group of synonyms may well include Septoria trijolii Ell. & Ev., 

 Septoria trijolii Cav., Ascochyta medicaginis Bres., Gloeosporium meliloti 

 Trelease, Ascochyta meliloti (Trel.) Davis, and Ascochyta lethalis Ell. & 

 Barth. 



Ascochyta imperjecta Peck on alfalfa is certainly different from this 

 fungus which occurs also on alfalfa. The former produces dark purple 

 spots which later become indefinite in outline and yellowed as contrasted 

 with the light-colored spots with a dark margin. Single spore cultures of 

 .4 . imperjec a differ from those of Stagonospora meliloti in being almost 

 black on oat agar instead of yellow. Sprague (1929:929) agrees that the 

 two fungi are different, for he says that " there can be little doubt that 

 A. imperjecta is different from A. medicaginis as shown by inoculation 

 work, coupled with study of material." Apparently Sprague did not 



