144 Some Factors In Plant Competition 



balance between the pots. Watering was done regularly, a similar 

 quantity being given to every pot on each occasion, so that the amount 

 of water available during the progress of the experiment was the same 

 in every case. 



Varying degrees of competition were induced by variations in the 

 rate of seeding, from one to five plants being raised in the narrow pots 

 containing 10 kilos of soil, and from one to eight in the broad pots with 

 20 kilos of soil. The pots were arranged in groups of five or eight (one 

 pot of each rate of seeding per group) and the groups were scattered 

 over the glasshouse on trucks to equahse conditions. When growth was 

 well established and the weather was favourable the trucks were run 

 outdoors into a wire cage. Mustard and barley were both tested, 10 

 narrow pots or 3 broad pots being used as a unit in every case. 



Experiment I. 

 Mustard. 



Narrow pots, 10 kilos soil. 



Seeds sown March 31st, 1917. One to five i)er pot after initial thinning. 



Plants cut May 29th, 1917. 



Very soon after the plants had emerged from the seedling stage it 

 was evident that the strength of development was in inverse ratio to 

 the number of plants per pot, and this relation became more and more 

 marked as time went on. The mustard was cut while most of the plants 

 were in full flower, though some had begun to go over into fruit. A 

 definite gradation of maturity occurred according to the number of 

 plants in the pot. The single 'plants (per pot) were very strong, sappy, 

 exceedingly tall and decidedly less mature than any others. The lower 

 leaves had begun to turn yellow but were not at all wilted and none had 

 dropped off. In most cases only the lowest flowers were fully developed, 

 the upper ones being in various stages of bud, while the axillary racemes 

 had hardly any flowers open. The five plants per pot were of medium 

 strength only, comparatively short, with stems inclined to be woody, 

 and were the most mature of all. The lower leaves had wilted and in 

 many cases had dropped off, so that they had to be gathered up for the 

 purpose of weighing. The flowers were fully out, and many on the main 

 stem had begun to form fruit. 



The 2, 3, 4 plants per pot showed a steady gradation between the 

 two extremes of I and 5 plants per pot. 



