The Polyporaceae of North America—lV. The Genus Elfvingia 
By WILLIAM ALPHONSO MURRILL 
The mycological field of Europe is small as compared with 
that of America. The European mycologist has in general a 
small country with limited variation in altitude, geological forma- 
tion and season, as well as a limited number of host plants, few of 
which are readily attacked by wood-loving fungi ; hence it is pos- 
sible to know more minutely the forms that do occur and to seg- 
regate varieties according to host, position and other details of 
which little note has yet been taken in America. The confusion 
of forms in Europe is largely due to former difficulties in travel, 
limited means, lack of interest in the work of others and lack of 
generalization, a condition of affairs accounted for to some extent by 
difference in language and the antipathy common among neighbors. 
Upon receiving an exotic plant, be it from Guinea or Greenland, 
the mycologist of limited outlook makes a heroic effort to corre- 
late it with some species growing in his immediate vicinity and, 
failing to do this, either loses interest altogether in the matter or 
half-heartedly looks up a name for it in some foreign flora. To 
send American fungi abroad for determination is usually to be 
either disappointed or deceived. To many European botanists, 
Kew is a very foreign country and America is off the map. 
One should not be surprised to find, therefore, that many 
American plants are parading under false names and that many 
are entirely new to the botanical public ; and what is true of species 
is likewise true of genera; the old molds must be recast and 
several new ones added to accommodate these large additions. 
For our northern forms, the work of recasting has been largely 
done by Dr. P. A. Karsten, of Finland, who has to deal with a 
local flora very similar to our own in its lines of cleavage, although 
the abundance of species present in our latitude is unknown in 
Finland. The basis of this similarity between North American 
and North European and Russian genera is found in the fact that 
these countries have been practically continuous so far as distri- 
bution is concerned, whereas the continents of the southern hemi- 
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