216 PLANT PHYSIOLOGY 



in permanent sterility. For this reason vitamin E is spoken of 

 as the reproductive vitamin. 



Vitamin F. — This vitamin, if one may predict in such matters, 

 is to be one of the vitamins into which B is at the present time 

 being split. The name seems to be settling on a growth-promoting 

 factor found in leaf vegetables and liver, but at the moment the 

 research in this field is too confused to be discussed in an ele- 

 mentary, general text such as this. 



Vitamin G. — After researches and disputes lasting over many 

 years, it has been concluded that pellagra is a deficiency disease 

 due to the absence of this vitamin. This disease occurs in the 

 southern United States, where corn and fat pork (with very few 

 vegetables) are the staple articles of diet. The symptoms are much 

 like those of beriberi, and it is, therefore, not surprising that this 

 vitamin was for a long time confused with vitamin B. It is water 

 soluble, and its chief sources are yeast, lean meat (especially 

 glandular organs), green vegetables dairy products, eggs, fruits, 

 and fish. 



The following table shows the general distribution of the vita- 

 mins as determined up to the present time (the figures indicate 

 relative richness) : 



Food Vit. A Vit. B Vit. C Vit. D Vit. E Vit. G 



Vitamins and Plants. — While it has been known that, with the 

 exception of vitamin D, vitamins are manufactured only by 

 plants, they have been studied chiefly from the point of view of 

 their effect upon animal nutrition. Whether they are equally 

 necessary for the nutrition of the plants which produce them, 

 remains to be shown, but the fact that the plant organs such as 

 fruits, leaves, and seeds, where metabolic processes are very 

 active, are the organs richest in vitamins, would indicate that they 

 do play a part in the economy of the plant. Although Lumiere 

 (1921) concluded that vitamins were not necessary for plants, 



