July, 1909.] 



47 



Miscellaneous. 



the reproductive cells contain A and the 

 other half a. Furthermore half the re- 

 productive cells bear B and half b. And 

 the characters of the original parents 

 do not stick together when the repro- 

 ductive cells are formed, but segregate 

 completely, so that the new combina- 

 tions Ab and aB are formed just as 



readily as the old ones AB and ab ; and 

 all these four sorts of reproductive 

 cells are produced in equal numbers. In 

 self-fertilisation--a process common in 

 plants— the four kinds of reproductive 

 cells meet at random, and the different 

 combinations which they form are shown 

 in the acconiuanying diagram — 



Pig. 1. 



In this diagram each square represents 

 an individual plant. The constitution 

 of each individual on the female side is 

 written above it, whilst the nature of 

 the male element which entered into its 

 formation is written on the left-hand side. 



Cross-hatched squares represent indi- 

 viduals with purple flowers, vertical 

 shading indicates red flowers, and hori- 

 zontal shading blue. It will be seen 

 that all purple flowered individuals 

 contain both the elements A and B. 



Red-flowered plants contain A and not 

 B, whilst blues contain B and not A. 

 One individuals out of sixteen contains 

 neither A nor B and has white flowers. 



It will readily bejseen that the propor- 

 tion in which the ^coloured individuals 

 occur is 9 purple : 3 red : 3 blue : 1 white- 



In actual practice when a very large 

 number of individuals is grown the pro- 

 portionate numbers found will approxi- 

 mate closely to some multiple of the 

 above. 



