DD 



DIAGRAM OF MENDEL'S LAW PARTICULARLY AS 

 JLLUSTRATED IN PROF. CORRENS'S CROSSING OF 

 MIRABILIS JALAPA ROSEA AND M IRABILIS JALAPA ALBA 



FIG. 33. Diagram showing Mendelian inheritance in Mirabilis jalapa. 



d D, deep rose parent, Mirabilis jalapa rosea .- the thick vertical stroke indicates 

 dominance of the deep rose-colour. R, White parent, Mirabilis jalapa alba ; the 

 thin horizontal stroke indicates recessiveness of the white colour. F l Hybrid off- 

 spring, light rose D(E) . The dominance of the rose was incomplete. G. Germ-cells 

 hypothetically segregated into pure deep rose and pure white ; their possible 

 fertilisations indicated by arrows. The male cells are to the right, the female to 

 the left. The fertilisation of two " homozygotes " or similar germ-cells indicated 

 by the arrow (1) yields (1) in the next generation F a extracted pure dominant : 

 the fertilisation of two homozygotes" indicated by the arrow (4) yields (4) in 

 the nest generation F a extracted pure recessive. The fertilisation of 

 " heterozygotes " indicated by the arrows (2 and 3) yield (2 and 3) in the next 

 generation F a impure dominants, which being inbred (self -fertilised) split up in 

 the next generation F s into deep rose, light rose, and white as before, in the pro- 

 portions 1:2 = 1. Note also that 1 in the generation P a yields a pure dominant 1* in 

 the third generation P* ; and that 4 in F 1 yields a pure recessive 4 A in the third 

 generation F\ 



[Facing p. 343 



