PHYSIOLOGICAL Kill.' I> UPON CULTURE MEDIA. 19 



producing cell l>ut a spore-bearing process of a cell, hence is properly 

 applicable to the narrowed apices of these verj cells. In the Latin 

 descriptions the term "basidium" has been retained, however. 



( 'onidia. — The usual data with reference to the conidia are of equal 

 service in our cultural studio, viz, shape, size, color, arrangement, 

 markings, mode of germination, and conditions of growth. A record 

 of the changes in color at different ages of the colony is essential. 

 Completeness in observation is as necessary in spore characters as 

 elsewhere. The variations in the size of conidia are notable in some 

 species : in others conidia appear to be either globose or elliptical, even 

 in the same chain. Where the outer cell wall is marked or spiny these 

 markings often do not appear until the conidia are fully mature. 



PHYSIOLOGICAL EFFECTS UPON MEDIA. 



Certain physiological effects of fungous growth which are incident 

 to the use of ordinary culture media have boon found to be reliably 

 characterisl IC of species. Some of these react ions are so conspicuous 

 a- to aid greatly in separating nearly related organisms. Such re- 

 actions a- have been found uniform and definite or unique are intro- 

 duced into the technical diagnoses of spceies in this paper. Other 

 physiological data are appended as accessory cultural information. 



Among t he data observed in repeated series of eomparat ive culture 

 are the following: Odor, litmus reaction of medium at different 

 stages of growth, liquefaction of gelatin media, the production of 

 coloring substances in the media, the changes produced in milk, and 

 the production of drops of transpired fluid upon surface of colony. 

 Am ong the accessory data, observations upon carbon assimilation, 

 upon proteolytic reactions, and upon the production of enzymes have 

 been made for certain species. 



Odor. — The production of definite odors by colonies is confined to a 

 small number of species, and even among these often to particular 

 media. When definitely present it is a character immediately recog- 

 nizable and in certain species diagnostic; in others it associates the 

 organism at once wit h a part icular group of species. 



Litmus. The use of an indicator in the medium gives in very 

 many species a sharp reaction. The value of this react ion is more nar- 

 rowly restricted, however, than is indicated in previous papers 

 (Thorn 25 : >. The in t roil net ion of sterilized litmus or azolitmin into 

 complex media brings contradictory results when the composition of 

 the medium is slightlj altered, [f, for example, a solution of puregela- 

 tin in distilled water be used as a nutrient .the reactions are definitely 

 alkaline, with very few exceptions, which are just as definitely acid. 

 The gelatin solution itself is acid. The alkaline reaction indicates 

 that t he products of t he digest ion of gelatin in such cases are of alka- 

 line nature. If. however, the gelatin solution be neutralized and 



