A DEMONSTRATION OF NUMEROUS DISTINCT STRAINS WITH- 
IN THE NOMINAL SPECIES PESTALOZZIA GUEPINI DESM. ^ 
Carl D. La Rue and H. H. Bartlett 
(Received for publication June 6, 1921) 
In the course of routine pathological work on the plantations of the 
United States Rubber Company, in Asahan, East Coast of Sumatra, we 
found that Pestalozzia was among the fungi most often isolated from diseased 
tissues of Hevea hrasiliensis . A comparison of several of the strains obtained 
showed that all were very similar as far as obvious characters were con- 
cerned, and all fell within the limits of Pestalozzia Guepini Desm., as this 
species has been broadly interpreted ; but they were quantitatively different 
from one another, and maintained their distinctness through successive 
generations. Since none of the diseases of rubber which have been at- 
tributed to Pestalozzia are particularly important, and since the time at 
our disposal was limited, only enough measurements were made to demon- 
strate that the nominal species in this group of fungi may be looked upon 
as composed of a large number of pure lines, each definable by its mode 
and range of variation. Looked upon in this light, the Fungi Imperfecti 
doubtless afford a parallel to the host of constant but hardly perceptibly 
distinct strains in some groups of the higher plants, such as Hieracium, 
in which the constancy of the lines is maintained because of the loss of 
sexual reproduction. The problem of species delimitation in either case 
is a most difficult one. Among many fungi the close restriction of strains to 
special hosts gives criteria for the separation of species which have never 
been differentiated morphologically, although in many such cases morpho- 
logical as well as physiological distinctions might often be established if 
more refined biometrical methods were used than those which prevail in 
systematic work. The truth of this statement, as well as the great ad- 
vances in mycology which may be expected to follow the more general 
introduction of biometrical methods, are illustrated by the notable studies 
of Stakman and Levine (i) in the rusts, and of Rosenbaum (2) in Phy- 
tophthora. 
Only morphological criteria, however, are available to the systematist 
in those weakly parasitic genera whose members are not confined to specific, 
or even closely related, hosts. This fact is coming more and more to be 
recognized, and mycologists nowadays much less often than formerly 
1 From the Botanical Laboratory of the Hollandsch-Amerikaansche Plantage Maat- 
schappij, Kisaran, Asahan, Sumatra, Published by permission of the United States Rubber 
Plantations, Inc. 
79 
