Inheritance in Tomato Hybrids. 



17 



the other characteristics. The hybrids were uniform in general 

 appearance. In the F 2 hybrids all the possible types visible 

 or recombinations of characters occurred, despite the fact that 

 we were able to grow to maturity only forty of these plants. 

 The theoretical proportions could not, of course, be secured, 

 since this is not possible with less than 64 plants. 



Eight visibly distinct types of plants are to be expected for 

 a trihybrid in the F 2 generation. These types are given in the 

 table below and a comparison is drawn between the theoretical 

 requirements for a Mendelian trihybrid and the actual propor- 

 tions secured. 





Expected for 64 



Actual for 40 Plants 



Plant Types 











Numbers 



Per cent 



Numbers 



Per cent 



Green foliage, red and round fruit 



27 



42 



15 



37.5 



Green foliage, red and pear fruit 



9 



14 



3 



7.5 



Green foliage, yellow and round fruit 



9 



14 



10 



25 



Yellow foliage, red and round fruit 



9 



14 



7 



17.5 



Green foliage, vellow and pear fruit 



3 



5 



1 



2.5 



Yellow foliage, red and pear fruit 



3 



5 



1 



2.5 



Yellow foliage, vellow and round fruit 



3 



5 



2 



5 



Yellow foliage, vellow and pear fruit „ 



1 



1 



1 



2.5 





64 



100 



40 



100 



It is seen from the above table that the actual results con- 

 form in a rough way with the theoretical requirements for a 

 trihybrid. The percentage approximation to the expectancy 

 is remarkably close for the small numbers of plants grown. 



GENERAL CONCLUSIONS. 



The studies of the tomato hybrids discussed in the preceding 

 pages lead to the following general conclusions : 



(1) . A large number of the attributes of the tomato, when 

 crossed with their complementary characteristics of differential 

 character unit pairs, exhibit in the first hybrid generation the 

 phenomena of dominance and recessiveness, and are subject in the 

 second hybrid generation to Mendelian splitting or segregation. 



(2) . These attributes exist as character units which are in- 

 dependent in heredity without respect to parentage. 



(3) . hi character unit polyhybrids the different character 

 units are usually independently heritable, and the recombinations 

 of characters occuring in the F 2 generation are in conformity with 

 Mendel's law for polyhybrids. 



