62 GROWTH HORMONES IN PLANTS 



first demonstrated in orchid pollinia, is probably identical with 

 the growth substance of coleoptile tips. The pollen of Hibiscus 

 also promotes growth in Avena (Laibach, 1932) . Sequoia pollen 

 has been found even more active than the pollen of orchids 

 (Thimann, 1934). 



Fruits and Seeds. — Growth substance has been demonstrated in 

 peas, beans, lentils, tomatoes, oranges, and lemons (Maschmann 

 and Laibach, 1933). Kogl, Erxleben, and Haagen Smit (1934, 

 Mitt. IX) isolated auxin a and auxin b from oil made from maize 

 embryos and from barley malt. Cholodny (19356) has reported 

 the presence of a growth-promoting substance in the hydrated 

 endosperm of sprouting oats and corn seeds which acts in the 

 same way as the growth hormone present in the coleoptile. 

 Using the lanolin-paste method, Laibach and Meyer (1935) found 

 that acid-alcohol extracts of both killed and germinating seeds 

 of Avena and Helianthus contained a substance that stimulated 

 growth of the Avena coleoptile; it was present in greatest con- 

 centration during early germination. It was present in high 

 concentration again at the time of fruit formation. The embryo 

 of Triticum also contains abundant growth substance (Thimann, 

 1934). 



Lower Plants. — The presence of a growth substance was first 

 demonstrated in lower plants by Nielsen (19306) when he showed 

 that two fungi, Rhizopus suinus and Ahsidia ramosa, produce it 

 when subjected to proper culture conditions. A series of investi- 

 gations concerning the nature of this fungus substance has led to 

 the conclusion that it is probably heteroauxin (Thimann, 19356). 

 The production of growth substance occurs generally among 

 bacteria (Boysen Jensen, 1931a). Besides two bacteria isolated 

 from saliva, the following are productive: Bac. mycoides, 

 Bac. suhtilis, Bad. xylinum, Bact. radiobader, Bad. dentrijicans, 

 Bad. coelicol., Bad. coli, Bad. vulgatus, Mycobad. album, 

 Mycobad. ladicola, and Proteus vulgaris. Sixteen of 20 investi- 

 gated bacteria formed growth substance. 



Besides those already mentioned, various other fungi are 

 growth-substance formers. Particularly large amounts are 

 produced by Aspergillus niger (Boysen Jensen, 19316). It has 

 been demonstrated also in baker's yeast (Nielsen, 19316), 

 Rhizopus Delemar, R. nigricans, R. tritici, and R. reflexus (Kogl 

 and Haagen Smit, 1931, Mitt. I), Boletus edulis (Nielsen, 1932), 

 and Penicillium (Guttenberg, 1933). In further studies, Kogl and 



