D 



B 



R 



_yv. 



(I) 



(lA) 



DD 



DD D(R) D(R) RR 



Q(.) F 



RR 



DIAGRAM OF MEN DELS LAW PARTICULARLY AS 

 ILLUSTRATED IN PROF. CORRENSS CROSS! NG OF 

 MIRABILIS JALAPA ROSEA AND MIRABILIS JALAPA ALBA. 



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



I', deep rose parent. Mirabilis jalapa rosea; the thick vertical strdke indicates dominance 

 of llie deep rose-colour. R, White parent, Mirabilis jalapa alba; the thin horizontal stroke 

 indicates recessiveness of the white colour. F' Hybrid offspring, light rose r)(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 t\vo" homozygotes" or similar 

 germ-cells indicated by the arrow fl) yields (1) in the ne.xt generation F^—e.\tracted pure 

 dominant; the fertilisation of two " homozygotes" indicated by the arrow (41 yields (4) in 

 the ne.xt generation F^— extracted pure recessive. The fertilisation of " heterozygoles" 

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

 nants, which being inbred (self-fertilised) split up in the next generation F^ int<j deep rose, 

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

 F^ yields a pure dominant 1* in the third generation F^ ; 



recessive 4'' in the third generation F^. 



and that 4 in F^ yields a pure 



[Facing p. 343 



