Individual Strength and Length of Fruit. 535 



been condensed by uniting the Individuals with simihir 

 thickness of stem, and by giving the mean length of theii 

 fruits. The number of individuals per group is given in 

 the last column. The length and thickness of the fruil 

 was measured on the lowest 20 fully developed fruits in 

 the case of each individual in the manner described above. 

 All the values are expressed in millimeters. 



The table brings out the strong correlation existing 

 between thickness of stem and thickness and length of 

 fruits. For, apart from negligible individual differences, 

 the fruits are longer and thicker, the thicker the stem 

 is. These figures are not sufficiently extensive for the 

 determination of Galton's value r;^ but they serve their 

 immediate purpose well enough. 



Taken in conjunction with the rest of what we know 

 about nutrition and growth in our plant they tell us that 

 as a rule the fruits are longer, the more vigorous the 

 plant is, and especially that the longest fruits are only 

 found on the strongest plants. Selection in the direction 

 of long fruits therefore chooses the strongest plants 

 whilst selection in the opposite direction must choose the 

 weakest.^ 



It should be mentioned here that manuring and the 

 choice of good seed are not the only methods of ensuring 

 the vigor of a plant. The distance of the plants from one 

 another, especially in youth, plays a very prominent part 

 in determining this. Plants standing alone usually grow 

 up very luxuriantly; the more plants one grows per 

 square meter the less vigorous are they. Another method 

 of effectively increasing the individual strength of the 



^ r = ratio = measure of correlation. 



^ It will be seen that this generalization agrees perfectly with the 

 considerations set forth in the critical part of this work. Cf. in this 

 respect, Papaver somnifcrum polyccphalum, pp. 137-140. 



