Mendel's law of heredity and horticulture. 



31 



Compound Characters. 



In many cases, however, the unit-factors do not happen to 

 correspond with the horticuUural characters, and interesting com- 

 pHcafcions then arise. For instance, in my experiments with 

 tomatos, red and yellow fruits behaved as units, red being the 

 higher and yellow the lower ; the presence of the ' ' red ' ' factor gave 

 a red tomato, while in the absence of the " red " factor the 

 tomato was yellow. But when the fiery red variety, ' Fireball,' was 

 crossed with the pale-yellow variety, ' Golden Queen,' four distinct 

 colour varieties appeared in the second generation (F,). There were 

 two kinds of reds and two kinds of yellows. This I found to be due 

 to the fact that the fiery-red colour of ' Fireball ' was really a com- 

 pound of two unit-factors, representing red flesh and yellow skin, while 

 * Golden Queen ' had yellow flesh and white skin. Consequently in 

 the second generation two new varieties arose by re -combination — a 

 carmine or " pink " tomato with red flesh and white skin, and a deep 

 yellow tomato with yellow flesh and yellow skin. In accordance with 

 the Mendelian expectation, a few individuals of these two new varieties 

 bred true, while others did not. 



The following diagram (fig. 17) will illustrate the results obtained 

 in this experiment : — 



Tomato 



F lERY Red Pa le Ye llqw 

 JL FiER.Y Red 



9 Fiery Red JCarmime Red 3DeepYellow 1 Pale Yellow 



^emoj^ S/C^ mAiU SfOm. ^/eMcm/ S/Hm. S/Cori. 



Fig. 17. — Showing the compound nature of the red fruit of the 

 ' Fireball ' Tomato and the appearance of two new forms by re-com- 

 bination FOLLOWING Mendelian Segregation. 



It will be observed that red flesh and yellow skin are both repre- 

 sented by higher factors appearing in Fi, while yellow flesh and white 

 skin are represented by lower factors which are not manifested in 

 F 1 , owing to the presence of the higher factors for red flesh and yellow 

 skin. 



