SUMMARY OP FRUIT STUDIES. 



73 



brought out between tliese two classes in the Bartlett and Buffum, 

 and quite pronounced differences in tlie Anjou, Angouleme, and Heatli- 

 cote. The tendency of the self-pollinated fruits is to be narrower and 

 not well filled out toward the blossom end. This suggests that the 

 stimulus to growth comes from the ovules, and when these are properly 

 fecundated they cause the development of the surrounding fruit. In some 

 varieties it is evidently not necessary that the ovules be fecundated 

 so as to grow into perfect seeds in order that the fruit may develop. 

 Most of the self-pollinated fruits were entirely seedless. It may be 

 questioned wdiether these fruits had their ovules perfectly fecundated. 

 Possibly the action of the X)ollen on the pistils stimulated the fruits to 

 develop without i)roperly fecundatiug the ovules. Focke* states that 

 there are two actions of the pollen, the one stimulating the ovary to 

 develop and the other fecundating the ovules, and that pollen which is 

 too foreign to the pistil may often induce the fruit to grow^ without 

 making good seeds. May not pollen wiiich is too closely related to the 

 pistil behave in the same way! Still another question comes up: 

 May not pears be produced in some cases without any pollen? Atten- 

 tion has previously been called to the fact that the pear is a false fruit 

 (p. 13), or rather that it consists of a true fruit with a thickened mass 

 of stem or leaves surrounding it. In the case of some plants, the Eng- 

 lish cucumber for instance,! it is thought to be true that the fruit with- 

 out seeds develops w^hen no pollen is applied. Several times in my own 

 work flowers were erhasculated and not pollinated, and with two excep- 

 tions uniformly failed to set fruit. Further, the large number of cases 

 in which the flowers not only required x^ollen, but even cross-pollen, show^ 

 with these varieties the necessity for fecundation. The two exceptions 

 occurred with the Le Conte and Heathcote. A few fruits set and were 

 counted on the Le Conte (p. 49) at Kochester, but none reached matur- 

 ity. Three fruits set on a Heathcote tree at Geneva and one of 

 these developed. It was just like the self-pollinated fruits (p. 70). 

 This of course may have been accidentally self-pollinated before the 

 flower opened. The possibilities of development without pollen need 

 to be further studied in the self-fertile varieties. It may be that these 

 varieties have the tendency to fruit so strongly inherent in them that 

 they do not alw^ays need the stimulus of pollen to make them grow, 

 but such cases are probably rare if they occur at all. It would be re- 

 markable if we should find that Avhile some varieties of pears require 

 cross-pollination the other extreme is reached by certain varieties in 

 that they do not require pollination at all, especially when we con- 

 sider that these so-called varieties are mere individual variations of an 

 exceedingly variable species. 



But to return to the comparison of the self-pollinated and crossed 

 fruit, the tendency of the former fruits was to be slightly later in 



* Die Pflanzeu Mischlinge, p. 447. 



t Munson, Secondary Effects of Polliuatiou, p. 44. 



