150 



Some Factors in Plant CoDipetition 



amount of soil and therefore twice the quantity of plant food was 

 available. This affords yet more conclusive evidence that under the 

 conditions of this experiment the amount of growth possible was strictly 

 dependent on the available nitrogen, irrespective of the number of 

 plants. A comparison of the figures for individual plants (Table V) shows 

 that the amount of dry matter produced and nitrogen extracted is 

 practically proportional to the amount of soil available and therefore to 

 the quantity of plant food, especially nitrogen, and also that a given 

 quantity of soil only admits of a given amount of growth. 



It is interesting to notice that while barley was able to extract 

 •20 gm. N from each tall pot, mustard only took away -14 gm. This 

 may be due to the longer period over Avhich the barley was grown, or 

 possibly to some essential difference in the absorptive action of the two 

 plants. 



Table V. 



* As the broad jjots contained twice as much soil as the narrow ones, each plant in 

 the broad pots %vith 2, 4, 6, 8 plants had the use of the same amount of soil as 1, 2, 3, 4 

 plants respectiveh' in tlie narrow pots. 



Table VI. Efficiency Indices. Barley. 

 For 10 tall pots. 



1 seed ])er 



2 



3 ' 



1 seed per 



2 



3 



4 



6 



6 



7 



8 



pot 



Range 



5-419— i-9m 

 4-796—4-578 

 4-431—4-023 

 4-151—3-927 

 4-021—3-858 



For S broad pots. 



pot 



5-933- 

 5-305- 

 4-952- 

 4-712- 

 4-536- 

 4-382- 

 4-256- 

 4-163- 



-5-708 

 -5-055 

 -4-876 

 -4-674 

 -4 431 

 -4-2.')4 

 -4-190 

 -4-130 



Avci'age efficiency index 



5-258 

 4-712 

 4-358 

 4-080 

 3-948 



5-852 

 5-225 

 4-922 

 4-701 

 4-483 

 4-334 

 4-214 

 4-147 



