314 SCIENCE AND FRUIT GROWING 



In the first place it was necessary to ascertain whether the 

 same number of plants when grown with and without root- 

 interference would behave in the same way. They should do 

 so, for the total soil available for growth would be the same in 

 both cases, and so would the total amount of toxin produced. 

 The results bore out this conclusion : thus 



Relative weight of 6 plants grown in 

 Divided Pots. Undivided Pots. 



Mustard . . . 100 100 



Tomatoes . . . 100 105 



Barley .... 100 98 



Tobacco . . . 100 113 



The difference is inappreciable, except in the case of tobacco; 

 and it is easily explained there by the spreading habit of the 

 roots in that case, which would put the plants grown in the 

 small compartments of the divided pots at a disadvantage. 



Root-interference, therefore, does not affect the results. The 

 next question was, does branch-interference affect them ? in- 

 cluding in the term "branch" all the above-ground growth of 

 the plants. To investigate this, three small plantations were built 

 up by means of the divided pots, so that the average distances 

 between the individual plants were 4 inches, 6 inches and 9 inches, 

 respectively. The average weights of the plants in the three 

 cases were found to be 



4" apart. 6" apart. 9" apart. 



Mustard . . . 100 116) 116^1 



ioo ii2/ II4 133! I2 4 



Tobacco . . . ioo 114 109 



Mean . . . ioo 114 119 



thus showing some advantage in separating the plants by more 

 than 4 inches, but only a doubtful further advantage by in- 

 creasing the distance between them to more than 6 inches. At 

 the same time, a comparison of the outer rows with the inner 

 ones in these (A, B in the table below) and in other similar 

 plantations of mustard (C and D), gave further evidence as to 

 the insignificance of the effect of branch-interference ; for the 

 comparison showed a smaller variation than what might reason- 

 ably be attributed to experimental error, and that variation was 

 not uniformly in any given direction. 



