246 



Prof. W. B. Bottomley. 



These facts indicate the possibility of the development, during germination, 

 of special growth substances which enable the young embryo to utilise 

 the food material present in the seed. If this is so, the removal of the 

 source of these growth stimulants by the cutting off of the seed as soon 

 as possible after germination should render the effect of an addition of 

 such substances in the food solution all the more marked. In order to test 

 this hypothesis, two series of wheat seedlings, similar to those used above, 

 but in a rather younger stage, were taken, and before the removal of their 

 seeds the two sets were of equal weight, viz. : 3'97 grm. Their seeds were 

 carefully removed, injury to the plants being avoided, and after this process 

 the two sets weighed respectively 3*2 and 317 grm. These were treated in 

 precisely the same manner as before, the first set being given complete food 

 salts, and the second food salts with the addition of the silver fraction from 

 bacterised peat. The weights of the two sets at various dates are shown in 

 the following- Table : — 



Table VII. 



Series. 



Weight of set of 18 plants. 



Percentage of increase 

 in weight. 



II. Complete food solution + silver 

 fraction from bacterised peat 



grm. 



After 16 days 3-37 



After further 17 days 3 "20 

 „ 2-85 



After 16 days 3 "63 



After further 17 days 4 -29 

 5-05 



per cent. 

 5-3 



o-o 



-10-9 



14 -5 

 35 -3 

 59 -3 



The following diagram shows the variation in weight of the seedlings 

 throughout the experiment, the dotted curve representing the series in pure 

 food, while the unbroken curve shows the effect of the addition of the silver 

 fraction. 



These results indicate that during the germination of wheat seeds certain 

 substances are formed which enable the young embryo to utilise the food 

 materials present. The supply of these substances formed by the seed during 

 germination is sufficient to establish the embryo as an independent seedling, 

 then some other source is necessary. It has been shown that these accessory 

 food substances are produced when peat — decayed vegetable matter — is acted 

 upon by certain soil bacteria, and the natural inference is that during the 

 bacterial decomposition of organic matter in the soil, that is, during humus 

 formation, these substances are formed, hence the beneficial effect on crops of 



