36 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. 



PHYSIOLOGY. 

 CULTURAL STUDIES. 1 



During the past three years the writers have had under observation 

 more than 4,000 cultures of the several species of Endothia on more 

 than a dozen artificial media, as well as on sterilized twigs of many 

 kinds. Throughout this work the writers have been impressed with 

 the uniformity of the behavior of the organism in culture and the 

 certainty with which the various species could be distinguished on 

 any of the media used. 



Cultures of Endothia parasitwa, ior instance, from specimens sent 

 from China or British Columbia were absolutely indistinguishable 

 from cultures made on the same medium from local material. 

 Transfers made from stock cultures which had been kept on artifi- 

 cial media for two years were identical with transfers from freshly 

 collected material. The same remarkable constancy held for the 

 other species. Cultures from material collected in different localities 

 or from different hosts were identical, not only in appearance but, so 

 far as the writers were able to determine, in temperature and moisture 

 relations also. As previously noted, this is in marked contrast to the 

 senior writer's experience with the species of Glomerella and it is 

 believed differs from the experience of many investigators of fungi. 



No less striking is the certainty with which the several species may 

 be distinguished on any medium tried. Endothia parasitica^ E. 

 tropicalis, and E. fluens and its variety mississippiensis are very 

 closely related morphologically. Moreover all except E. parasitica 

 have, as near as could be determined, much the same relation to their 

 hosts. Yet each species has distinctly and readily recognized charac- 

 ters on culture media. 



It should not be imagined, however, that the differences are 

 recognizable at once as clearly distinctive characters. The differences 

 at first glance might readily be considered fluctuating variations. 

 But the fact that the characters remain constant through hundreds 

 of generations and have never varied toward one another makes 

 them worthy of recognition as specific characters. 



In a previous paper (77) the writers described their results with 

 cultures of Endothia parasitica, E. fluens, E. fluens mississippiensis, 

 and E. gyrosa on a number of culture media. At that time the work 

 of other investigators was reviewed and the methods of preparing 

 the various culture media and making the cultures described. Since 

 the publication of that paper, However, cultures of two more species, 

 E. tropicalis and E. singularis, have been secured and about 2,000 

 additional cultures of the various species made. In addition to the 

 culture media mentioned in the previous paper (77, p. 10), the writers 



1 The cultures described were all grown at ordinary laboratory temperatures in the 

 winter, about 20 to 24 C. 



