102 GROWTH HORMONES IN PLANTS 



nitrate-citric acid solution, in some experiments without growth 

 substance, in others with it present in concentrations of 0.9, 9.0, 

 and 21.0 WAE per 100 cc, respectively. After being cultured for 

 11 to 14 days at a temperature of 16°C., the mycelium was 

 removed, dried, and weighed. It was found that the addition 

 of growth substance always resulted in retardation of growth — in 

 one case by as much as 50 per cent ; in other cases, by significantly 

 less. This is in agreement with the results of Nielsen and 

 Hartehus (1932), who found that rhizopin was without influence 

 upon respiration or the production of dry matter in Aspergillus 

 niger (see Nielsen, 1931a). Biinning (1934a, h) also found no 

 furthering influence of the ether-soluble hormone of Aspergillus 

 upon production of dry substance in this fungus. Biinning, 

 Schopfer (1935), and others have shown the growth-stimulating 

 effect of other substances on lower organisms. Schopfer reported 

 that extracts from wheat embryos, orchid and other pollens, etc., 

 stimulate the growth of numerous Mucorineae. Pure crystal- 

 lized vitamin Bi promotes the growth of Phycomyces in such 

 small amounts as 0.00057 per cubic centimeter of the culture 

 medium. However, the extracts with which Schopfer has been 

 working contain active substances which are not to be confused 

 with the growth substances treated at length here. 



Animal Cells. — Since substances capable of promoting growth 

 in plants can be extracted from animal sources, it is of interest to 

 find out whether these substances have any influence on animal 

 growth. 



According to the investigations of Fischer, the growth of heart 

 fibroblasts in tissue cultures is not increased by auxin a or 6 (see 

 Kogl, Haagen Smit, and Tonnis, 1933, Mitt. VIII), nor is the 

 metamorphosis of tadpoles influenced by the addition of auxin 

 (Kogl, Haagen Smit, and Erxleben, 1933, Mitt. VII; Sylven, 

 1933). Navez and Kropp (1934) obtained similar negative 

 results when they appUed the plant-growth hormone to crustacean 

 eyestalks; i.e., there was no activation of the chromatophores. 



Plant-tissue Culture. — LaRue (1935) removed pieces of the 

 embryos of half-grown seeds of Taraxacum, Lycopersicon, 

 Lactuca, etc., and cultured them on nutrient agar. White's 

 (1934) culture solution was used but without the yeast extract. 

 In Lactuca, complete plants developed from 0.5 mm. pieces of 

 embryonic hypocotyl. Successful growth took place only in 



