246 THE VITAMINS 



degree of greenness in edible plant parts and their content of vita- 

 min A. 



Quinn and Cook (1928) in quantitative studies of the vitamin A 

 content of white and yellow yautia showed the latter to be over ten 

 times as rich in vitamin A as the white variety. 



Hauge and Trost (1928, 1930) reported a close physiological rela- 

 tion between vitamin A and the yellow endosperm kernel character in 

 maize. In the process of crossing and segregating yellow and white 

 dent maize they found vitamin A associated exclusively with the yellow 

 endosperm, and not with the white, even in kernels of corn secured 

 from the same ears. The genetical factors responsible for yellow pig- 

 mentation and vitamin A occurrence could not be separated as it was 

 not possible to secure any demonstrable transfer of vitamin A to grains 

 possessing pure white endosperm. This association was further con- 

 firmed when in hybrid red maize, vitamin A was found only in kernels 

 possessing yellow endosperm. The color of the pericarp was found to 

 be without effect in the formation of vitamin A in the kernel. It appears 

 that the genetical factor responsible for carotinoid pigmentation is also 

 responsible for vitamin A formation. In testing two types of corn, 

 YYY and Yyy, possessing as wide a range of yellow endosperm char- 

 acter as possible, it was found that the vitamin A content parallels very 

 closely the yellow endosperm character. "The critical level for Yyy 

 corn is approximately 15 per cent while that of the YYY corn is about 

 five per cent. Seven per cent of YYY corn gave good growth while it 

 took 20 per cent of the Yyy corn to give comparable results. It is appar- 

 ent that the YYY corn contains approximately three times as much 

 vitamin A as the Yyy corn which is also the same ratio as the genetical 

 character of the yellow endosperm. These studies show that the physio- 

 logical relationship between yellow endosperm character and vitamin A 

 content is very close in maize." 



Pointing out that the early negative results of tests of the vitamin 

 A activity of pigments had been obtained before the recognition of 

 vitamin D, v. Euler and his colleagues (1928, 1929) reported that of 

 the lipochromes yielding a blue color reaction with arsenic chloride, two 

 — carotene and dihydro-a-crocetin — promoted growth in vitamin-A- 

 depleted rats. It is of special interest that the active dihydro-a-crocetin 

 had been prepared by reducing the biologically inactive a-crocetin with 

 titanous chloride. Moore (1929) also found carotene (m. p. 174° C. 

 in air) active and did not regard the active material as a mere con- 

 taminant. A carotene (m. p. 174 to 178° C. ; iodine number 330) ob- 

 tained by Collison, Hume, Smedley-MacLean and Smith (1929) from 



