236 PHYTOHORMONES 



hormones, the question as to what name should be given to 

 their growth-promoting substances remains in doubt. The 

 term vitamin has the definite connotation of a food factor 

 absorbed from the medium, while these growth substances 

 are in some cases produced by the organisms themselves. 

 On this account Kogl (1935) was led to term bios a phyto- 

 hormone, because although yeasts require bios for growth, 

 they also have the ability, though not usually in sufficient 

 degree, to produce bios for themselves. According to Hux- 

 ley's nomenclature (1935) we should name such substances 

 local or intracellular activators. 



The reason why these growth substances have been men- 

 tioned here is because there are some interesting parallels 

 between them and the phytohormones. The group includes 

 bios, vitamin Bi, " Wuchsstoff B," and the substances active 

 on bacteria and protozoa. Vitamin Bi is necessary for the 

 growth of a few yeasts and numerous fungi. Wuchsstoff B 

 is the term given by Nielsen and Hartelius (1932) to a sub- 

 stance, insoluble in ether, produced by Rhizopus cultures and 

 active in promoting growth of Aspergillus. (The name should 

 not be confused with auxin b.) Apparently both an organic 

 growth substance and a group of accessory inorganic sub- 

 stances are involved (Nielsen and Hartelius, 1933). 



The term bios is specifically restricted to substances active 

 in promoting the growth of yeasts. Bios is of particular 

 interest here because it was the first example of a system 

 of interlocking substances, the action of each of which is 

 increased by the presence of the others. That any one bios 

 produces an effect alone is probably to be ascribed to the 

 presence within the cell of small amounts of the other 

 factors. The work of the Toronto school has shown that 

 bios consists of at least 3 fractions, of which bios I was 

 shown by Eastcott (1928) to be z-inositol, and another, 

 bios II, has recently been isolated, under the name of 

 "biotin," by Kogl and Tonnis (1936). Like auxin, biotin 

 is active at extremely high dilution, 1 part in 4 X 10^^ of 

 solution having a detectable effect; however, in terms of 



