April, 1915.] The Inheritance of Size in Tomatoes. 489 



The average weight of fruit the F-3 parent, plant 10, is 2.22 

 grams while the F-4 generation possessed an average fruit-weight 

 of 2.215 grams — a remarkable similarity between weight of parent 

 fruit and the average weight of fruit of offspring. It is further 

 to be noted that six fruits are lighter and five fruits are heavier 

 than 2.22 grams, so that there is as equal a variation as fruit-size 

 as possible in the offspring on each side of this parental fruit- 

 weight. This relation between parent and offspring is graphically 

 shown on Plate XXII. 



Over 700 fruits were harvested from 74 plants in this series of 

 experiments. This data is summed up and the relationship 

 between the parental and hybrid fruit-weights is shown on 

 Plate XXII. 



INTERPRETATION OF RESULTS. 



When the results, which were obtained, are interpreted it 

 should be clearly kept in mind that the recorded weights represent 

 the average fruit-weight of a single plant and not the weight of a 

 single fruit. In practically all of the known experiments along 

 this line the individual fruit-weights have been used as a basis for 

 study and these weights have been shown in the tables of results. 

 There is no evidence to show, in a number of experiments, at least, 

 that any special care was observed in the selection of fruits, which 

 seemed to be taken at random from a hybrid generation or a pure 

 line of plants. The fluctuation in size of fruit on each plant; the 

 difference in the number of fruits produced on each plant ; and the 

 variation in the length of the fruit-bearing period render the 

 results secured by such harvesting liable to considerable error. 

 On the other hand, when an accurate record is kept of each fruit 

 and the average fruit-weight of each plant, more accurate results 

 (especially the generation average based on the fruit-weight of 

 the plants) are bound to be obtained. 



There are only a few recorded experiments which deal com- 

 prehensively with the subject of the inheritance of size of fruit in 

 the F-1 generation. This scarcity of data, taken together with 

 its complexity, render the correct analysis of this problem very 

 difflcult. Especially has there been a great deal of discussion 

 among scientific men as to whether the F-1 fruit-sizes approach 

 more nearly to the geometrical or to the arithmetical mean between 

 the parent sizes. 



Groth, basing his statement upon linear dimensions, reports 

 that the size of the F-1 tomato fruits is the geometric means 

 between the parents. In this view he is supported by Bruce who 

 had previously obtained like results with tomatoes. The data 

 presented in this paper also shows that the F-1 fruits of the 

 tomato (currant-pear cross) are the geometric means between the 

 parental sizes. 



