166 Some Factors in Plant Competition 



Table XIV. Efficiency Index of spaced plants. 



The efficiency indices of the spaced plants cover a comparatively 

 small range (Table XIV), while the interquartile range is very small. 

 The lowest quartile includes all those plants which from one cause or 

 another are weaker than their fellows, and the variation in efficiency of 

 these plants is greater than that of all the rest. This indicates an 

 approach to a certain standard of efficiency in the majority of the plants 

 — i.e. that under the prevaihng conditions in the greenhouse a certain 

 quantity of growth is possible in the given time, and a large proportion 

 of the spaced plants approximate to this standard. The increased 

 deviation on the part of the minority may be due to the somewhat 

 excessive insolation referred to earlier in this paper, which would tend 

 to depress the growth of any plants that were naturally at all weakly. 

 The variation in the rate of growth of the spaced plants may therefore 

 be attributed to the different response of the individuals to their environ- 

 ment when they are not influenced by the proximity of other vegetation 

 and are therefore free from competition. 



The efficiency indices of the crowded plants reveal a very different 

 state of affairs. The total range is very large, 2- 199-4-989 per cent, per 

 dayi — and the interquartile range runs from 3-831-4-729, a far wider 

 deviation than in the spaced plants. The average efficiency of the 

 crowded plants as thus shown is lower than that of the others, and the 

 approximation to the standard growth is considerably less. 



Table XV. Efficiency Index of crowded plants. 



Range Difference in range 



Total range *3-012— 4-989 1-977 



Interquartile range 3-831— 4-729 -898 



First (lowest) (luartile *3-012— 3-811 -799 



Second quartile 3-831—4-304 -473 



Third fiuartile 4-353—4-729 '376 



Fourth (upper) quartile 4-734—4-989 ^ -255 

 * The index of the very weakly plant (2-199) is omitted. 



' 2-199 is the index for the one excei)tionally weak plant in the series, but even if 

 this is rejected the range runs 3-0l2-4^989 per cent. ])im- day 



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