SOLANACEjE 589 



Extensive experiments made by Fletcher and Gregg with 

 greenhouse or forced tomatoes showed that self-fertilized 

 blossoms set fruit as well as cross-fertilized ones. Further- 

 more, there was practically no difference in the appearance 

 or weight of the fruit, and no difference in the number of cells. 



Parthenocarpy. — This phenomenon is not at all uncommon 

 in tomatoes. By this is meant the ripening of the fruit 

 without the fertilization of the ovules. Such fruits, of 

 course, possess no germinative seeds. 



Abnonnal Tomatoes. — Munson has found, in crossing 

 tomatoes, that the amount of pollen placed on the stigmas 

 affects the size of the fruit. Two stigmas -in the same flower 

 cluster were given different amoimts of pollen: one abun- 

 dant pollen, the other 10 to 20 grains. With plenty of 

 pollen, normal fruit resulted, while with scanty pollen, small 

 and deformed fruit resulted. In the first case, there was 

 abundant seed, while in the latter, only a few seeds. One- 

 sided tomatoes result when pollen falls upon one side of the 

 stigma only. It is midoubtedly commonly true that small 

 and irregular tomatoes are caused by an insufficient supply 

 of pollen. 



The Mature Fruit.^ — The fruit is a true berry (Fig. 240). 

 The wild form of our common garden tomato {S. esculenlum) 

 has a two-celled fruit with a rather dry placenta. The cells 

 are definite in both number and shape. Cultivated forms 

 of the common garden tomato have a number of cells in the 

 fruit ; they are indefinite in both number and shape, and the 

 placenta is exceedingly fleshy. The fewest celled fruits are 

 considered nearest the original type. The pear and cherry 

 tomatoes both have two-celled fruit. The calyx is persist- 

 ent, adhering to the base of the fruit. The fruit varies in 

 shape, color, and smoothness of surface. The seeds are 

 numerous and small. 



