Plant Qrowth'Suhstances 



prunings, such as are usually discarded as valueless, which had 

 developed well-marked roots after being "skewered" during 

 March and April, 1937, into a compost heap formed largely of. 

 grass and turves. 



Root-induction and cell-elongation are distinct. Zimmer- 

 man, Hitchcock, and Wilcoxon (1936) recorded that "so far, 

 no growth-substances have been found to accelerate elonga- 

 tion in root-tissue. This peculiar response of roots raises the 

 question whether there might exist in nature an entirely 

 different type of hormone effecting elongation of the cells." 

 Thornton and Nicol (1936) noted that elongation of one type 

 of cell — the root-hairs of leguminous plants — was induced by 

 secretions of legume nodule bacteria. Some properties of 

 these secretions have been examined, but their chemistry is 

 still obscure. Bottomley (1915-17) found that legume nodules 

 were a potent source of auximones. 



Vitamins 



J. Bonner and Greene (1938) (with D. Bonner) have pub- 

 lished figures of the vitamin B^ content of three samples of 

 cattle manure; they found o -08-0 -13 mg. of vitamin Bj per 

 kilo, of dung. A laboratory culture of Azotobacter, the free 

 living nitrogen-fixing bacterium frequently present in fertile 

 soils, contained over a thousand times as much. Since vitamin 

 Bj (thiamin, aneurin) seems to have a potently favourable 

 effect on the growth of normal plant-roots, these findings may 

 be important. The authors do not quote the pioneering work 

 of Mockeridge (1920), but they say that the "long-disparaged 

 'auximones' of Bottomley" (1914, 1915-17) seem to rest upon 

 a sounder basis than has been hitherto admitted. 



V. G. Lilly and L. H. Leonian {Science, 1939, 89, 292) 

 have reported a demonstration of vitamin Bj in soil. 



Vitamin C was first used to accelerate root-production on 

 cuttings [Salix, willow) by Davies, Atkins, and Hudson 

 (1936), who found it to act similarly to indole-acetic acid, 

 while less toxic. See also p. 43. 



68 



