124 T O R R E Y A 



structing any portion of the vitamin. For example, Aspergillus niger has com- 

 plete synthetic power for thiamine ; it can make this substance if supplied with 

 sugar and minerals including nitrates. On the other hand, Phytophthora cin- 

 nanionii must be supplied with thiamine as such. It apparently lacks the ability 

 to synthesize any portion of the thiamine molecule, resembling the animal in 

 this respect. Between the two extremes of no synthetic power and complete 

 synthetic ability, there exist many types of incomplete synthetic power. For 

 example, Mucor ramannianus can make the pyrimidine half of the thiamine 

 molecule but not the thiazole portion ; Sclerotium rolfsii can make the thiazole 

 but not the pyrimidine part ; Phy corny ces can combine the two intermediates 

 into the thiamine molecule but is incapable of making either. 



The impo7'tance of studies on vitamins in relation to plants. By this time 

 you may be willing to admit that plants need vitamins, but you may still 

 question the importance of such knowledge, particularly when you remember 

 what I have said on the negative results of applying vitamins to green plants 

 in field or garden. If most plants make all the vitamins they need, why should 

 w^e study the subject? 



There are many reasons. Even though vitamin B^ seems at present to 

 exist in sufficient amounts in green plants to permit them to develop satis- 

 factorily without giving them more of it, there are many other vitamins, some 

 as yet unidentified, and w^e know relatively Httle of their relations to the 

 growth of green plants. If we search further, we may perhaps find a vitamin 

 not made by green plants in large enough quantity for their maximum devel- 

 opment — one which when fed to the plant will actually perform part of the 

 miracles our commercially-minded friends have told us could be accomplished 

 with vitamin Bi ; but, at present, this seems like a rather long chance. 



However, it is quite necessary for us to understand the nutrition of bac- 

 teria, yeasts and molds, a good many of which suffer from vitamin deficiencies. 

 These lower plants are most important in causing disease and decay as well 

 as bringing benefits through their relation to fermentation, cheese making and 

 many similar processes. If we wish to control these lower plants — limit their 

 detrimental activities and encourage their beneficial properties — we must un- 

 derstand how they live. For example, the edible morel is one of the most de- 

 licious of fungi, far superior to the mushroom we buy in the markets. Yet no 

 one has ever cultivated it. Why? Perhaps it suffers from vitamin deficiencies 

 which have never been properly satisfied by the materials upon which men 

 have tried to grow it. 



But even if further research should show that the use of vitamins on 

 plants is of no practical significance, the study of the relation of vitamins to 

 plants is important because of the light it may throw on their uses for animals. 

 Plants have been found to be valuable tools in determining the presence and in 



