FORMATION AND OCCURRENCE OF AUXINS 63 



it appears to be principally in the fatty substance between 

 the pollen grains. The extracts from a number of different 

 pollens were analyzed for their auxin content by Thimann 

 and Went (1934). The activities found were very variable, 

 Hicoria being the highest. Sequoia pollen was also shown 

 by Thimann (1934) to be rich in auxin. 



On the presence of auxin in seeds there is some difference 

 of opinion. Cholodny (1935) found that auxin was absent 

 from Avena seeds, but appeared as soon as the seed had 

 taken up some water. ^ From then on the amount rapidly 

 increased and then decreased again, completely disappear- 

 ing in 48 hours. The auxin production was found to be in 

 the endosperm and not in the embryo, which, in fact, 

 appeared to absorb it. Pohl (1935, 1936) has also found 

 that if Avena seeds are punctured and placed in water, auxin 

 diffuses out into the water. Apphcation of an e.m.f. across 

 the seed increased the diffusion into the water, and the auxin 

 accumulated at the anode. The growth rate of shoots from 

 seeds so treated was greatly reduced (c/. below). 



Kogl, Erxleben, and Haagen Smit (1934), using water 

 extraction, found great variation in the auxin content of 

 Hordeum seeds; in the ungerminated seeds the amounts were 

 extremely small, but during the germination of most varieties 

 the amounts increased up to the 5th day, the highest value 

 reached being 0.42 mg. per kg. They found, however, that 

 maize germ oil, which is prepared from_ ungerminated Zea 

 Mays seeds, is rich in auxins, and they were able to isolate 

 two of the pure substances from a sample of maize oil which 

 contained about 0.7 mg. per kg. The authors' own ex- 

 periments have shown that some samples of wheat germ, 

 wheat germ oil, corn meal, and rice polishings often contain 

 considerable amounts of auxin, up to 4 mg. per kg. being 

 found (c/. Thimann, 1934). 



On the other hand, the data of Laibach and Meyer (1935) 

 cited above, show that the auxin content both of Zea Mays 



1 On account of its possible role in germination he suggested the name " Blasta- 

 nin," but since the activity was determined on Avena it falls under the definition 

 of auxin. 



