EVOLUTION 



383 



Here the mode of the first poppy is 8 and of the second 

 1 1. Now it will be clear to the reader that the mode is 

 not for a small series like these poppies a very good 

 method of determining the most frequent number of stig- 

 matic bands. For the transfer of a single capsule from 

 the 1 1 to the i o group of bands in the case of the 

 second poppy would have rendered the mode inde- 

 terminate ; the transfer of two such capsules might have 

 transferred the mode even to 10. For this reason the 

 average value of the character is very frequently taken 

 as determining the type instead of the modal value. The 

 first poppy has capsules with 8.50 stigmatic bands on 

 the average, the second with 10.75. These numbers 

 would be taken as giving the individuality of these two 

 plants for this character. For the beech trees the average 

 number of ribs on the leaf is for the first tree 17.54 and 

 for the second 15.08, and these may also be taken as 

 giving the type of leaves on these two trees. 



Now suppose we proceed further and take a large 

 number of leaves from a considerable number of beech 

 trees, and a great number of capsules from wild poppy 

 plants, but pay no attention to the individual trees or 

 plants. We shall then have simply beech leaves and 

 poppy capsules representing the race characters and not 

 types of individuals. Here are results for 2600 beech 

 leaves and for 2268 poppy capsules : — 



Beech Leaves. Frequency of Different Types of Leaves 



