537 
Food Substances for Plant Growth . 
The slow growth of the seedlings in this experiment will be noted. 
This is accounted for by the fact that they were grown in an unheated 
greenhouse on the roof of King’s College from late in February to early in 
April this year, when there was very little sunshine. 
Up to a certain point the two series of plants increased in weight to an 
almost equal extent. Beyond this point the seedlings growing in pure 
food solution were unable to utilize the food supplied to them, and 
gradually withered and died, whilst the seedlings with the silver fraction 
of bacterized peat extract continued to grow, and were strong and healthy 
throughout the experiment, their vigour being specially manifest in a well- 
developed root system. It is evident from this experiment that bacterized 
peat contains a substance or substances which enable the plant to utilize 
the normal mineral food constituents supplied to it. In nature doubtless 
this substance or substances are supplied by ‘ humus ’ — the decayed organic 
matter in the soil. 
A series of experiments by Fiirst ( 10 ) in 1912 on the anti-scorbutic 
accessory food substances obtained from various seeds is suggestive in 
connexion with the fact noticed above, that in both series of plants growth 
was almost equal up to a certain point. 
Fiirst showed that it was only during germination that the anti-scorbutic 
substances were developed in seeds of.barley, oats, peas, and flax. Guinea- 
pigs suffering from scurvy when fed on these seeds before germination soon 
died, but seeds, soaked in water for twenty-four hours, and then kept in 
a warm room for two or three days until the young roots began to show, 
were as effective in curing the disease as extracts from green vegetables. 
The development of these substances during germination must have 
a definite relation to the seed itself, and suggests the possibility of the 
formation during germination of special growth substances, which enable 
the young embryo to utilize the food material present in the seed. If this 
is so, the removal of the source of these growth substances 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 state, were taken. Before 
the removal of their seeds these 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 3-17 grm. 
These were treated in precisely the same manner as before : the first being 
given complete food salts, and the second food salts with the addition of 
the silver fraction. The weights of the two sets at various dates are shown 
in the following table : 
