Theory of Plant Breeding 



hoary nature of the leaves and the colour of the flowers. 

 This last may be due to a colouring matter in the sap 

 or to a yellow tinge in the colour of the plastids, so that 

 four distinct conditions are possible. RC when both 

 sap and plastids are coloured, re when both sap and 

 plastids are uncoloured, and Re or Cr when one or 

 other of the colours is present. 



It was found also that hoariness is due to the presence 

 of two (H and K) complementary factors, and only 

 manifested itself when both C and R were present as 

 well as H and K. 



The unravelling of this curious tangle of hybrid char- 

 acters is most ingenious and gives one a very good idea of 

 the complicated nature of hereditary transmission. 



This is not at all an exceptional case, for colours are 

 often produced by the combination of various shades. 

 Thus when Mr. Hurst experimented with a red tomato 

 (" Fireball ") and the yellow-fruited " Golden Queen," 

 he found that there were at least four kinds of fruits. 

 In the " Fireball " the red flesh shows through a bright 

 yellow skin, whilst in " Golden Queen " the flesh is yellow 

 and the skin is white. Amongst his hybrids were reds 

 with a white skin and yellows with a yellow skin. 



So that the four different sorts of fruit can be ex- 

 plained simply by the presence or absence of red in 

 the flesh and of yellow in the skin. 



With orchids, of course, one would expect, as experi- 

 menters have found, many strange contrasts and new 

 tints formed by the combinations of their many colour- 

 ing matters. 



Why should one character always be the dominant 

 one ? There has been no satisfactory explanation of 

 this. Of course when it is the very common case of 

 the presence or absence of a colour, then presence will 

 dominate and absence will be recessive. 



Yellow and green are rather interesting examples of 



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