388 FUNGOUS DISEASES OF PLANTS 



that the spermogonial, aecidial, uredo, and teleuto stages are respec- 

 tively represented by O, I, II, III, and it is here unnecessary to 

 consider the fifth or sporidial stage ; the types, then, are as follows : 



En forms with all stages; or O, I, II, III present. 



Brachy forms with secidia omitted; or O, II, III present. 



Opsis forms with uredo omitted; or O, I, III present. 



Hemi forms with spermogonia and aecidia omitted ; or II, III present. 



Micro forms with teleutospores only ; or 1 1 1 present, germinating only 

 after a resting period. 



Lepto forms with teleutospores only; or III present, germinating im- 

 mediately. 



It is interesting to note that in the far North or in Alpine 

 regions, as Fischer shows, the micro and lepto forms predominate. 

 ^Ecidia occur alone in considerable number, and also hemi forms. 

 Many hemi forms, particularly in such genera as Uromyces and 

 Puccinia, have been insufficiently investigated, and will doubtless 

 prove to be c?i forms, mostly hetercecious, that is, eu-hetero forms. 



No terms applicable alike to all genera having similar spore 

 forms, based upon some common root and the prefixes above 

 mentioned, expressing also hetercecism and autcecism, have been 

 suggested. It seems desirable for many reasons to employ as this 

 root the word uredo, and since it will be used in combination with 

 these prefixes, there can scarcely be any confusion, although uredo 

 is a form-genus name. With this nomenclature a form which is 

 eu-hetercecious will be termed euheterouredo, and the other combi- 

 nations will be made in an analogous manner. 



II. FAMILIES AND GENERA 



According to Fischer the order may be most conveniently sub- 

 divided into four families, and the characters employed as a basis 

 of this system of classification are for the most part those of the 

 teleutospores. 1 



1 Arthur has proposed for the Uredinales an entirely new system of classifica- 

 tion (Resultats scientifiques du Congres International de Botanique, Vienne, 1905, 

 pp. 331-348). By this system many more genera would be constituted since, in 

 addition to the usual characters, the completeness of the life cycle with respect 

 to the four main stages is made generically diagnostic. He has also introduced 

 the terms pycnium, <zcium, uredinium, and telium in substitution for spermogonial, 

 aecidial, uredo, and teleuto stages. 



