318 SCIENCE AND FRUIT GROWING 



obtained was practically the same, whether there were six or 

 only three plants in the pots. But in the intermediate cases, 

 where the plants were of different degrees of vigour, some factor 

 other than partition of the food-contents must have come into 

 play; the whole of the food-supply was not exhausted, and less 

 plant-growth was obtained than where either six or three plants 

 of equal vigour were present : there must have been some 

 factor preventing the plants from utilising the whole of the 

 food-supplies available. Will the existence of a toxic action 

 explain such a result ? 



It is an incontestable fact that every plant has some limit to 

 its possible development; from which it follows that equal 

 increments in either favourable or unfavourable conditions 

 such as equal doses of manure or of toxin will have less and 

 less effect on the plant, the larger that plant is. 1 Where two 

 plants of different sizes are growing side by side, a certain pro- 

 portion of the toxin formed by one will make its way to, and 

 will act on, the other, and whatever extra dose the weaker plant 

 thus obtains, the stronger will lose. But the deduction of a 

 given dose from the stronger plant will have less effect in increas- 

 ing its growth, than will the addition of a similar dose have in 

 diminishing the growth of the weaker plant : hence the result 

 will be that the combined growth of the two plants will be 

 reduced owing to their being of unequal vigour. This exactly 

 tallies with the facts observed. 



Such results, whilst affording valuable additional evidence in 

 favour of the existence of toxic action, have, also, an important 

 bearing on practice. If half the seeds at a sowing lag behind 

 the others in their germination, even by four days only, the 

 reduction in the total crop eventually obtained will be as much 

 as 22^ per cent. (155, instead of 200) at any rate in the case 

 of mustard. The importance of uniform germination in the 

 seed-bed is, therefore, great. Unfortunately, seeds are not at 

 present tested according to this uniformity, and the farmer or 

 gardener can do nothing to secure it, beyond seeing that the 

 conditions in the seed-bed are as uniform as possible. It follows, 

 also, from these results that to attempt to make up for deficient 

 germination by a later sowing amongst the earlier plants, will 

 only produce weaklings, and injure those plants which are 



1 It is held that for every additional ton of dung supplied to a mangold 

 field, an additional ton of produce will be obtained. If true at all, this 

 can be only approximately true, and within very narrow limits : a mangold 

 will not be infinitely small if grown without dung, nor infinitely large if 

 grown on a dung heap. 



