PEARS. 



123 



Fertility and Sterility. — The object of the cul- 

 tivator of Pears and other hardy fruits is first 

 to secure good trees, and secondly to obtain 

 regular crops of the best fruit. As regards the 

 subject of these remarks, the first object is some- 

 times much more easily attained than the second, 

 because apart from climatal and seasonal ad- 

 verse influences, other causes occasionally inter- 

 fere with the production of fruit. The two 

 principal causes of infertility in Pears are de- 

 fects in the essential organs of the flowers and 

 excessive luxuriance of growth, and each of 

 these is of so much importance that they merit 

 a somewhat full discussion, together with the 

 remedial measures that can be adopted. 



Imperfect fertilization owing to the defects 

 in the flowers of Pears has not been so fre- 

 quently observed here as in hotter or drier 

 climates, such as in the United States, but it 

 does occur here and is very perplexing to 

 growers whose trees appear in excellent health, 

 and produce flowers freely year after year, yet 

 rarely set a crop of fruit. If the failure is due 

 to weakness or to the opposite extreme — undue 

 vigour — it is possible to find a remedy; but in 

 the other case — the simple failure of flowers — 

 it seems more difficult to understand and to 

 deal with. The fact is that some Pears, like 

 Apples and other fruits, become at times par- 

 tially sterile mainly through the failure of the 

 pollen, and as this is by no means constant, 

 i.e. it may vary from season to season and in 

 different localities, it has led to several careful 

 investigations with a view to finding effectual 

 remedies. It seldom occurs in a plantation 

 containing several varieties of Pears, and is 

 principally found where large quarters are de- 

 voted to one variety. The obvious remedy in 

 such cases being the same as suggested for 

 Apples, namely, planting those that do not set 

 their fruit well in alternate lines with other 

 good cropping sorts. The whole subject has 

 been carefully and thoroughly studied by Mr. 

 M. B. Waite, assistant pathologist to the United 

 States Department of Agriculture, and the re- 

 sults of his observations and experiments were 

 issued in 1898 in the form of an elaborate 

 report on The Pollination of Pomaceous Fruits, of 

 which the general conclusions are summarized 

 as follows :— 



1. Many of the common varieties of Pears 

 require cross -pollination, being partially or 

 wholly incapable of setting fruit when limited 

 to their own pollen. 



2. Some varieties are capable of self-fertiliz- 

 ation. 



3. Cross -pollination consists in applying 

 pollen from a distinct horticultural variety, 

 that is, one which has grown from a distinct 

 seed, and not in using pollen from another 

 tree or the same grafted variety, which is no 

 better than that from the same tree. 



4. Self-pollination takes place no matter 

 whether foreign pollen is present or not. The 

 failure to fruit with self-pollination is due to 



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Fig. 924.— Flowers of Pear (Beurre d'Amanlis). 



sterility of the pollen and not to mechanical 

 causes, the impotency being due to lack of 

 affinity between the pollen and the ovules of 

 the same variety. 



5. Varieties that are absolutely self -sterile 

 may be perfectly cross-fertile. 



6. The condition of nutrition and the general 

 environment affect the ability of the tree to set 

 fruit either with its own pollen or with that from 

 another variety. 



7. Pollen is transported from tree to tree 

 by bees and other insects and not by the wind. 



8. Bad weather during flowering-time has 

 a decidedly injurious influence on fruitage by 

 keeping away insect visitors and affecting the 

 fecundation of the flowers, and, conversely, fine 

 weather favours cross-pollination and the setting 

 of the fruit. 



