506 Prof. W. B. Bottomley. Effects of Auximones on 



germination of seeds. Brown* has shown that during the germination of 

 barley seeds, certain soluble nitrogenous substances, which are essential for 

 the early stages of development of the young plant, are formed in the 

 endosperm and absorbed by the embryo. The writer also has found that a 

 water extract of germinated seeds has a similar effect on Zemna plants 

 growing in culture solution to that of bacterised peat, while no growth- 

 promoting substances could be obtained from dry seeds. It is probable, 

 therefore, that the seedlings used in the ordinary water-culture experiments 

 may already contain the necessary minimal quantities of organic substances 

 requisite for ordinary growth, but that a further supply of these substances 

 is essential for optimum growth and development. It is therefore not 

 unreasonable to assume that organic growth-promoting substances are as 

 essential for plant as for animal nutrition, since the difference in metabolism 

 between plants and animals is one of degree only ; and that just as the plant 

 is indebted to the bacterial activities of the soil for the nitrogen which it 

 passes on to the animal in elaborated form, so the growth vitamines which 

 the animal obtains from the plant are not entirely manufactured by the 

 plant as such, but are, at least partially, the products of bacterial activity in 

 the soil in which the plants are growing. 



Sum mary. 



1. Raw peat, when further decomposed by means of aerobic soil organisms 

 — " bacterised peat " — -is found to contain certain growth-promoting substances 

 (auximones). 



2. Zemna minor plants cannot maintain growth for any length of time in 

 culture solutions containing only mineral nutrients. 



3. The presence of soluble organic matter is essential for complete growth. 



4. The addition to the mineral culture solution of 368 parts per million of 

 organic matter from the water extract of bacterised peat resulted, after 

 six weeks, in a multiplication of the number to 20 times, and an increase in 

 weight to 62 times, that of the control plants. The water extract free from 

 humic acid, representing an addition of 97 parts of organic matter per 

 million, gave 9-|- times the number and 29 times the weight ; 32 parts per 

 million from the alcoholic extract gave 3£ times the number and 7^- times 

 the weight ; 13 parts per million from the phosphotungstic fraction gave 

 1-| times the number and 2h times the weight. 



5. The effect of the reduction in amount of auximones with successive 

 fractionation of the bacterised peat was also manifest from the general 

 appearance of the plants. Those in mineral nutrients only decreased in size 



* Brown, H. T., 'Trans. Guinness Kesearch Lab.,' vol. 1, \x 288 et seq. (1906). 



