167 



species a course that I have already followed in the case of Colletotri- 

 chum (115) and which was followed by Elliott (53) in dealing with Al- 

 ternaria. 



My H. No. 1, H. No. la, H. No. 16, H. No. Ic, and H. No. Id, the cause 

 of foot-rot in Madison county, 111., as well as my Helminthosporium num- 

 bers 3-9, 11-19, 22-27, 34, 37, 38, 42, and 43, all belong to the same general 

 type and are characterized by a conidium that tapers toward each end from 

 a point of greatest thickness which is nearer to the base than to the apex 

 of the conidium. The conidia are therefore not typically cylindrical or 

 even subcylindrical. While all of these numbers agree in general type, 

 many of them differ somewhat from others in the collection. Thus Nos. 1 

 and 3 differ as is shown in Plates IX, XI -XII I, and, so far as observed, 

 in this character only, and only under the conditions described. Others 

 differ in modal spore-length or septation, in distinctness of zonation, or in 

 other minor colony-characters (PI. IX). Number 13 differs slightly even 

 from No. 14, though both are derivatives from the same original culture; 

 and the same may be said of Nos. 15 and 16. These differences which now 

 actually exist, are probably due to unconscious selection of saltants in trans- 

 ferring from tube to tube. All of the numbers listed above which show 

 constant, though but slight, differences from other numbers I regard as 

 elementary species, the Jordanons of Lotsy. They need not be further 

 characterized or differentiated than has been done in previous pages. One 

 of these elementary species, H. No. 3, is derived from an Iowa culture prob- 

 ably identical in character with that from which Pammel, King, and Bakke 

 described H. sativum, and this culture, No. 3, still agrees essentially with 

 their description. All of this group of elementary species may therefore 

 be regarded as belonging to the Helminthosporium sativum group, or Lin- 

 neon. The question of the possible identity of this group with the H. teres 

 and H. sorokinianum groups I shall not now discuss further than to point 

 out that so far as can be judged from the picture of H. sorokinianum given 

 by Sorokin (107) that species is not characterized by longitudinally eccen- 

 tric conidia; also that subsequent to the publication of the species H. sati- 

 vum, Bakke (6) states that "cultural experiments have determined that the 

 disease is due to Helminthosporium teres Sacc." He adds: "He [Dr. Ravn] 

 further substantiated my opinion that the disease was due to H. teres and 

 similar to what had been so prevalent in Denmark during the years 1898 

 and 1899." Bakke, in a foot-note, however, adds: "A. G. Johnson, of 

 Madison, Wisconsin, considers H. sativum and H. teres distinct forms." 

 Saccardo, who examined H. sativum, sent to him by Bakke, expressed the 



