Inheritance in Tomato Hybrids. 



1 1 



more than one pair of character units. In the production of the 

 hybrid races we endeavored to select for mother plants varieties 

 thoroughly established in type. Plats of the mother varieties 

 were grown and observed during the two years the work was in 

 progress, and in every case the offspring from the self-bred plants 

 proved to be constant and uniform in heredity. Four plants 

 each of the F 1 generation of hybrids were grown in the green- 

 house and twelve plants each of this generation were grown in 

 the field the following summer as controls. Seeds were selected 

 from the greenhouse plants of the Fj generation for the F 2 hybrids 

 to be grown in the field the following year. Care was used 

 throughout the work to prevent crossing and the admixture 

 of foreign forms. 



RESULTS OF CROSSING. 

 Inheritance of Particular Characteristics. 

 In the twenty-one distinct variety crosses made in these 

 experiments thirteen differential pairs of unit characters were 

 involved. When any one of these character unit pairs is con- 

 sidered by itself we find dominance of one character of the pair 

 in the first generation and segregation of the original units in the 

 second generation in approximately Mendelian proportions. 

 Since there is uniformity of behavior in inheritance for all of 

 the characters studied, it will not be necessary to describe each 

 character unit cross in detail. The behavior of the pear and 

 apple fruited hybrids will serve as an illustration for all. 



Pyrijorm x Roundish Fruit. 



The pyriform character of tomatoes is correlated with the 

 corolla structure of the flower, the tube being relatively long and 

 narrow. In pear tomatoes the corolla often persists until torn 

 asunder by the lateral pressure of the developing fruit, and thus 

 the constriction at base of neck is accentuated. The round 

 fruited varieties, on the contrary, invariably possess a short, 

 though relatively large, corolla tube. It is evident then that 

 we are here dealing with the conditions of neck and no neck, 

 characteristics which can be coupled definitely with well defined 

 floral structures. 



Five distinct crosses were made between pear varieties 

 (with fruit having well developed neck) and round or apple 

 fruited sorts. In some of these crosses the pear character be- 



