COMPARATIVE CULTURAL DAI \. 87 



iii ammonium nitrate. Aside from data as to growth or failure to 

 grow, culture in such a medium is fruitless. 



Cohn's solution is also an acid medium, but its acidity is due to 

 the presence of monopotassium phosphate (KH a P0 4 ). In a series 

 tit' cult i ncs wit 1 1 Dox's formula it was shown thai the monopotassium 

 phosphate had practically do different effeel upon cultures of these 



species than the dipotassium phosphate (K 2 HP0 4 ). 



Very few of the species were found to gro\* typically upon Cohn's 

 solution, however, although nearly all germinated. Comparative 

 work with Dox's formula shows that bul few of the species studied 

 are capable of normal assimilation of carbon from forms of tartaric 

 acid. Only three of the species experimented with failed to show 

 distinct germination. One of these inoculated with V. camemberti 

 var. rogt ri, remained four months without exhibiting any germination 

 of the conidia. The conidia were then transferred with a platinum 

 needle to a pet ri dish of gelatin; under these conditions the same 

 spores developed into typical colonies without showing any ill 

 effects of four months' immersion in the fluid which they were unable 



to assimilate. 



In solutions nontoxic in character many species exhibit definite 

 selective preferences for nutrient elements in particular chemical 

 combinations. This selective adaptability to particular forms of 

 nutrients differs greatly for different groups of species. Some 

 forms of wide distribution seem adapted to produce typical growth 

 upon quite varied chemical solutions. Other species (e. g., the rots 

 of citrus fruits ), equally w ide in t heir dist ribution, are closely depend- 

 ent upon particular forms of food, whereas between these extremes 

 are many forms exhibiting preferences as to nutrients yet capable 

 of development, although more slowly, in media containing nutrients 

 in forms assimilated with difficulty. These experiments have offered 

 no tangible evidence of rapid adaptation in media found unadapted 

 at first to development. Such power of gradual adaptation is not 

 excluded, however, by these experiments. 



COLOB IN CONIDIAL AREAS. 



In dealing with all species it has been found by repented experi- 

 ment that the green color of the spores is dependent upon the proper 



assimilation of the carbon element. Many of these species produce 



a brighter green when canesugar is present than with any other 

 form tried. Grown upon gelatin, or upon potato agar or bean agar 

 (free from sugar), several species produce green masses of conidia 

 which rapidly become some shade of gray, brown, or almost black 

 in media without sugar, but when cane sugar is present they are 

 deep green and remain unchanged for much longer periods. Certain 

 other species entirely lack green color except when sugar is present. 



