i64 BREEDING 



tall factor, and the other half the dwarf factor ; the 

 tall factor has not been adulterated with dwarfness 

 by its union with a dwarf factor, nor the dwarf by 

 the tall. The two kinds of factors occurring in equal 

 numbers amongst the germ cells of the hybrid are 

 as pure, in respect of the character they represent, as 

 the same two factors existing in the germ cells of 

 the parental tails and dwarfs, according to the theory. 

 Assuming this to be true, what result would be 

 expected to follow from the self-fertilisation of such 

 a hybrid ? Let us be perfectly clear, before we 

 attempt to answer this question, as to what we are 

 considering. On the one hand there are all the ovules 

 in all the flowers on a plant, amounting, if the plant 

 has been given plenty of room to grow, to anjrthing 

 between two and five hundred ovules ; half of these 

 ovules are supposed to contain tall factors, and the 

 remaining half, dwarf factors. On the other hand, there 

 are all the pollen grains on the plant. The numbers of 

 these must be immense, and I know of no estimate 

 of their number in a single flower ; nor is the matter 

 of any importance for our purpose. Suffice it that 

 the number of them is vast. Half of these pollen 

 grains are supposed to contain tall factors and the 

 remaining half dwarf factors. I shall speak of pollen 

 grains as synonymous with the male germ cell, to 

 avoid circumlocution. What is the result of the 

 fertilisation of these few hundred ovules by the few 

 hundred pollen grains necessary for the purpose ? 

 Let us consider first the ovules with the tall factor. 

 They have an equal chance of being fertilised by a 



