48 SYSTEMATIC J'OMOLOGY 



iinicli iiilci-t'st to llic I'ruit-^rowcr, t'crl ili/at ion incites remark- 

 al)l(' <;r()\v1li in llic rct'optaclc and jx'dicd so lliat what is popu- 

 larly called a fruit may be a true fruit plus the much chan^'od 

 receptacle or flower-stalk. The pulpy part of the strawberry 

 is an enlarged receptacle and the so-called fruits of the apple 

 and pear are the modified receptacles and flower-stalks. 



After fertilization, the corolla and usually the style, including 

 the stigma, wither and may so remain on the growing ovary, 

 or more often fall ofl^. The base of the style in some varieties 

 of apples develops into fleshy tissue which alters the shape of 

 the calyx -tube in the ripened fruit. In a few varieties of apples, 

 the remnant of the style forms a more or less fleshy point in 

 the mature fruits called the pistil-point. In some varieties of 

 grapes the stigma adheres to the apex of the fruits, a distinguish- 

 ing mark worth noting. 



77. Abnormal fruits. — The student of systematic pomology 

 must make note of abnormal fruits, for which there may be 

 various causes. Lack of proper fertilization is a common cause 

 of malformed lopsided fruits of apples, pears, and strawberries. 

 It has been demonstrated many times by observation and ex- 

 periments that w^hen certain stigmas in apple, pear, and straw- 

 berry floAvers have been pollinated and others not, the fruits 

 from such partly pollinated flowers are unsymmetrical as only 

 the pollinated carpels produce seeds, and the parts of the fruits 

 possessing these grow much more rapidly than those in which 

 the carpels are seedless. The experiments of several workers 

 show that, while only one pollen-grain is necessary to fertilize 

 an ovule and so produce a seed, when more pollen is supplied 

 the resulting fruits are so stimulated as to be larger. 



78. Self-sterile and self-fertile fruits. — Some varieties of 

 pome-, drupe-, and vine-fruits are characterized by self -fertility, 

 others by self -sterility, still others by a condition somewhere 

 between. AVhile these cases are of small significance in sys- 

 tematic pomology, they are of prime importance to the fruit 

 grower and should always be noted in describing varieties if 

 the condition is known. Self-fertility and self-sterility vary 

 greatly in accordance with climate. The pollen of some fruits 

 will fertilize flow^ers of other varieties of the same species when 

 another set of varieties wdll not. Some varieties are said, there- 



