[Vol. 1 

 190 ANNALS OF THE MISSOURI BOTANICAL GAUDEN 



the study necessary for the application of the generic definition 

 may be sure ninety-nine times out of a hundred that the fungus 

 on which he is working is a Siereum, for example, and not a 

 Thelephora, nor a Cratcrcllus, nor a Cladoderris, nor a Corticium, 

 nor a Pcniophora, nor a Sehacina. It is an obligation on authors 

 to group their species so accurately under genera that Stereum, 

 for example, shall comprise all the species of this genus known to 

 science, and no others. The synonomy of species in later pages 

 will show how vaguely the genera of Thelephoracece have been 

 comprehended. 



It is desirable that a genus should consist of but few^ species 

 in those cases where the group is sharply and naturallj^ set off 

 from others, that is, w'here no intermediate species connect the 

 genus with other groups. While such small genera are desir- 

 able, if wholly natural, it is in the highest degree objectionable to 

 create small artificial genera by arbitrarily segregating the 

 species of a natural genus and so establishing indefinite lines 

 of demarkation between genera. Under such a procedure the 

 generic location of certain species becomes W'holly arbitrary 

 and always continues as a stumbhng block for new students 

 and this leads to the loading of our literature wdth so-called new 

 species. A case in point is Saccardo's scheme in the 'Sylloge 

 Fungorum' in which he separates Hypochnus from Corticium 

 and Peniophora without any natural generic planes of cleavage. 

 In practical work one needs to know exactly what the generic 

 limits of Corticium, Peniophora, and Hypochnus are. The 

 question naturally arises as to just how^ loose and open the 

 structure of the fructification must be to be included in the 

 genus Hypochnus rather than in Corticium or Peniophora. 

 Henning's violation of the principle involved is still more fla- 

 grant, for he separated the Hypochnacece as a new family from 

 the ThelephoraceoB^ and placed Hypochnus of Saccardo in the 

 Hypochnacece, and Corticium and Peniophora in the Thelephora- 

 cece. As all students of the Thelephoracece have found Hypoch- 

 nus, as understood by Saccardo, wholly unw^orkable, it would 

 increase the usefulness of the 'Sylloge Fungorum' if Saccardo w^re 

 to distribute among Corticium and Peniophora, the species 

 which he now includes under Hypochnus. 



»Englcr unci Prantl, Nat. Pflanzenfam. (I. 1**): 114. 1898. 



