[Vor. 1 
192 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
species which I have placed in the genus Peniophora because 
of the presence of cystidia students may look for under Corticium 
when, by а more hasty study of their collections, they fail to 
detect these organs. Оп the other hand, students using more 
discriminating methods than mine may detect cystidia in species 
in which I have overlooked them, and such students will search 
in Peniophora for species which I have placed under Corticium. 
Species intermediate between genera always cause such trouble. 
There are many intermediates between Peniophora and Cortic- 
тит, yet in this particular case the advantage from the separa- 
tion undoubtedly more than compensates for the disadvantages 
occasioned by the intermediate species. 
The case of Peniophora has been considered at length, be- 
cause this genus is being regarded as a precedent for subdividing 
Stereum and grouping under Lloydella all those species which 
have conspicuous non-sporebearing organs between the basidia. 
Such a separation, however, would be artificial and give rise to 
a troublesome series of intermediate species, without the com- 
pensating advantage which accrued in the case of Peniophora 
and Corticium. Stereum is not a genus of difficult species nor does 
it comprise an immense number of species. It is just a fine, nat- 
ural group of species capable of being more sharply defined 
than it was by Fries, so as to receive some species from Тһе- 
lephora of Fries and to part with some toCorticium. So defined, 
even beginners will have no trouble in recognizing species of 
Stereum. Systematic work in mycology should strive to estab- 
lish and maintain just such natural, clean-cut genera as Sterewm. 
It seems to me best to work along constructive rather than 
destructive lines. Fries had a wonderful ability for the per- 
ception of the natural grouping of fungi on the basis of gross 
morphology and habit. Since his time, research has greatly 
enlarged the knowledge of the internal structure of fungi and of 
the organs of propagation. The value of such organs in the 
classification of seed plants is well known. It is feasible to 
modify somewhat the genera of T'helephoracem as defined by 
Fries, in accordance with the true relationships and differences 
shown by the present knowledge of internal structure, basidia, 
and spores, and a system results which is the natural evolution 
of taxonomic and morphologic study of T'helephoracem. This 
