D 



i) 



(2)®. ®0) 



DD 



0(4) 



0M 



RR 



DIAGRAM OF MEN DELS LAW PARTICULARLY AS 

 ILLUSTRATED IN PROF. CORRENSS CROSSING OF 

 MIRABILIS JALAPA ROSEA AND MIRABILIS JALAPA ALBA. 



Fig. 33— Diagram showing Mendelian inheritance in Mirabilis jalapa. 



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 1 Hybrid offspring, light rose D(R). 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 ill in the next generation F — extracted pure 

 dominant: the fertilisation of two "homozygotes" indicated by the arrow (4 1 yields (4) in 

 the next generation F 2 — extracted pure recessive. The fertilisation of " heterozygotes " 

 indicated by the arrows (2 and 8) yield (2 and 3) in the next generation F a - impure domi- 

 nants, which being inbred (self-fertilised (split up in the next generation F s into deep rose, 

 light rose, and white as before, in the proportions 1:2:1. Note also that 1 in the generation 

 F* yields a pure dominant 1* in the third generation F* ; and that 4 in F- yields a pure 

 recessive 4* in the third generation F". 



[Facing p. 343 



