244 CHEMISTRY OF PLANT LIFE 



has no vitamines of other plant origin in it. The addition of 

 barley wort, containing the vitamines from barley germs, or any 

 other similar supply of vitamines, induces rapid growth and the 

 storage of vitamines in the growing yeast masses, (c) The growth 

 of many bacteria is either wholly dependent upon or greatly stim- 

 ulated by the presence of vitamine-like substances in the medium 

 upon which the micro-organisms grow, (d) Sclerotinia cinerea, 

 the brown rot fungus of peaches and plums, will grow only in a 

 medium which contains, in addition to the essential sugar, salts, 

 and nitrogenous material, vitamines derived from either the 

 natural host plant tissues or other plant sources. These may be 

 of two types (namely, a vegetative factor and a reproductive 

 factor) or two different manifestations of activity of the same 

 vitamine substance. But both of these factors must be pro- 

 vided before the fungus can make its characteristic growth. 



There is, as yet, no conclusive evidence on many of the matters 

 concerning the relation of vitamines to plant growth. But it 

 seems that these substances are of almost universal occurrence in 

 the organic world; that they are not of the same general type as 

 other substances which are essential to the nutrition of plants or 

 animals, but have specific stimulating or regulating effects upon 

 the physiological activities of the organism; that the vitamines 

 which are essential to animal life are elaborated by plant tissues, 

 but that in the case of the bacilli of certain human diseases there 

 seems to be some indication that the affected tissues of the animal 

 host produce vitamines which are essential, or favorable, to the 

 growth of the parasitic organism. There seems, therefore, to be 

 evidence of a mutual relation between plants and animals with 

 respect to their nutritional needs for the so-called " vitamines." 

 But the evidence concerning the function of these substances in 

 the tissues of the organism which elaborates them is, as yet, inad- 

 equate to provide any clear conception of the reason for their 

 development or of the mechanism by which they are elaborated. 

 Neither is there, as yet, any conclusive evidence concerning the 

 chemical nature of the substances themselves. 



AUXIMONES 



Certain investigations have indicated that bacteria, at least, 

 develop exogenous vitamines which are beneficial to the growth of 



