396 Jounml of Agriculture, Victoria. [10 July, 1917. 



tbe stamens and pistils are weakened, the pollen partly impotent, 

 and the trees' vitality impaired during the blooming period. 



3. The natural weakness or imperfection of the structural for- 

 mation of the flowers or impot«ncy of the pollen. 



4. The insufficiency of fluid in the stigmas to insure the ger- 

 mination of the pollen grains and to facilitate the elongation of 

 the pollen tubes. 



5. The stigmas assuming the receptive condition before the 

 pollen is ripe, or vice versa. 



6. The planting of varieties on unsuitable soils or under un- 

 favorable' climatic conditions. 



7. The neglect of inter-planting sterile sorts with varieties suit- 

 able for interpollination. 



8. The want of bees, in or near the orchard, as a cross-pollinat- 

 ing agency by which cross-fertilization is greatly facilitated. 



That Nature, in animal life, abhors inbreeding is reflected in the 

 weak bodily condition and general imperfect constitution of the speci- 

 mens resulting from a too close blood relationship of the parents form- 

 ing the union. The law which governs animal reproduction, in this 

 respect, is also applicable in a marked degree to the fertilization of the 

 blossoms of fruit trees, and, to some extent, in plant life generally. 



The stigmas, in obedience to this law, mostly repel, or endeavour 

 to repel, the pollen from their own flowers, and even that from the 

 flowers of a different tree of the same variety. 



Cross-fertilized flowers invariably set a heavier crop of better-shaped 

 fruits, which contain larger numbers of fully-developed seeds, than 

 those self-fertilized. 



Continual heavy rains, accompanied by comparatively low tem- 

 peratures and intermittent frosts during the blooming, practic- 

 ally prevent the setting of all varieties; but these conditions, even in 

 localities which favour them, are rare. Dry, hot wdnds, on the other 

 hand, reduce the quantity of fluid in the stigmas and encourage the 

 development of Thrip (Thrips tahaci), which often destroy tbe reproduc- 

 tive organs of late-blooming varieties and prevent their setting. 

 Medium temperatures with occasional light showers, afford ideal con- 

 ditions during the blooming period. 



Generally speaking, of the early-blooming sorts, the Jonathan, par- 

 ticularly when cultivated under the conditions which produce rank 

 growth, is one of the most noticeable of those which comply freely 

 with Nature's law relating to reproduction by retaining its self-sterility. 

 It has been found, however, that when grown on the lighter, well- 

 cultivated and manured, sweet, Siluran soils, this variety often liberally 

 meets the orchardist's requirements by producing heavy crops of fruit 

 without the aid of a cross-fertilizer. Consequently, when dealing with 

 this subject, it is advisable to generalize rather than to dogmatize. 

 However, as it is known that cross-fertilization increases the quantity 

 and improves the quality of the fruit, it is advisable on every occasion 

 to interplant even to meet the contingency of possible self-sterility. It 

 is obvious that, when planting cross-fertilizers, varieties of high com- 

 mercial value should be selected in preference to those of inferior 

 quality. 



