412 



ENCYCLOPEDIA OF PRACTICAL HORTICCLTL'RE 



eties of plums are self-steiile; Waite (U. 

 S. Division of Vegetable Pathology, Bull- 

 etin 5) shows results of many experi- 

 ments carried on with the pear to show 

 the affinity of certain varieties for the 

 pollen of certain other varieties. Some of 

 the most interesting discoveries made by 

 Waite are. that the descriptions given by 

 "Warder, Thomas and Downing were true 

 only for the fruits resulting from cross- 

 fertilization; that the fruits from cross- 

 fertilization were much larger and that 

 the flavor was much better in the crossed 

 varieties than the fruits resulting from 

 self-fertilization. 



Everyone has noticed that isolated fruit 

 trees failed to bear fruit though they 

 blossomed full each year. The Wild 

 Goose plum is a very good illustration of 

 this self-sterility in fruit trees, familiar to 

 everyone who has planted this variety in 

 isolated positions. 



This self-sterility, as it is called, is the 

 inability of the pollen of a plant to fer- 

 tilize its own ovules or those of other 

 plants of the same horticultural variety 

 and is indicated in fruit trees by the con- 

 tinued dropping of the fruiting organs be- 

 fore the fruits have become well formed, 

 although fruits often drop from other 

 causes, as frost, general debility of the 

 tree, etc. 



No one can say why a variety should 

 refuse its own pollen and accept that of 

 another variety. Accepting Darwin's law 

 that "Perpetual self-fertilization is injuri- 

 ous and results in inferior and less fertile 

 offspring." we would admit, that, in the 

 countless ages of the selection of the 

 apple, inferior offspring and, perhaps, the 

 entire loss of fertility has been avoided 

 by self-sterility. In the apple, self-fertil- 

 ization has been guarded against in differ- 

 ent ways, as will be seen in the descrip- 

 tions and experiments which follow. 



Detiiiitioii of Terms Used 



Self-sterility: Inability of pollen to 

 fertilize ovules of same horticultural 

 variety. 



Self-fertile: A plant is said to be self- 

 fertile when the pistil will accept i)ollen 

 from a plant of the same horticultural 

 variety. 



Cross: Union of pollen cell and ovule 

 of two distinct horticultural varieties. In 

 no case is it meant the transfer of pollen 

 from one flower to another on the same 

 tree or from one flower of a variety to the 

 pistil of another individual tree of the 

 same horticultural variety. 



Pollination: Act of transferring of 

 pollen to the pistil. 



Fecundation: Union of pollen cell and 

 the ovule. 



Fertilization: A general term to in- 

 clude both the preceding terms. 



The flower of the apple is regular and 

 perfect in all of its parts; petals and 

 sepals five, petals varying in color from 



FiK. 1. Xo. 1. Oulleu Stamens Before Dehisr- 

 ins. No. 2. CuUen Outer Row of Stamens 

 Dehisced. 



a pure white to a faint rose: stamens 20 

 or less, filaments of two lengths, one set 

 of anthers ripening later than the other 

 (see figure I), anther two-celled dehiscing 

 along the outer margin, the two cells not 

 always dehiscing at the same time but 

 the dehiscance of both taking place within 

 a very short period; pistils ripening be- 

 fore the stamens, stigma extremely papil- 

 lose and in a condition to catch and retain 

 pollen before it is receptive, though it is 

 in a receptive condition as soon as the 

 flower opens; stigma secreting a sticky 

 fluid which also aids in holding pollen 



