316 



SCIENCE AND FRUIT GROWING 



per pot, with mustard it held good with anything over about 

 16 plants to the pot. 



Tobacco. 

 Weight of plants . 



Mustard. 

 Weight of plants . 



These results may be expressed by the statement, that, in a 

 limited amount of soil, the weight of a plant is proportional 

 to the area occupied by it, or to the square of the distances 

 of the plants from each other. 



Weight per \ 



plant / 



Height of \ 



plants / 



FIG. 45.- 



124 



70 



114 



80 



-MUSTARD PLANTS EXHIBITING THE DKAWING- 

 UP EFFECT OF CLOSE PLANTING. 



Though root-interference does not affect the growth of a plant 

 when all the plants are of the same age and vigour, it might do 

 so if they differed in these respects. To examine this, three 

 plants were sown, both in divided and undivided pots, on a given 

 date, and another three were sown in each pot 20 days later : but 

 the results were found to be not comparable ; for the first sown 

 plants in the undivided pots, owing to the larger amount of earth 

 available, made much more growth than those in the divided 

 pots. To correct this source of error, the interval of 20 days 



