122 THE PLUM IN KANSAS. 



of self-sterility among varieties of plums has by no means been ap- 

 preciated or even suspected. His tabulation shows that of 6428 blos- 

 soms covered, on fifty-six varieties, representing all classes of plums, 

 only jBve produced fruits, and from the experiments he draws the con- 

 clusion that "for all practical purposes, all classes and varieties of 

 native plums may be regarded as absolutely self-sterile." It is possi- 

 ble that these results might vary with different seasons and in differ- 

 ent localities, but, making due allowance for possible variations, the 

 results are startling enough to warrant the attention of plum growers 

 everywhere. The cause of this sterility appears to lie largely in the 

 inefficiency of the pollen of the flowers of a plant upon the stigmas 

 of the flowers of the same plant. It lies in a condition known to ex- 

 ist among many wild as well as cultivated plants. One of nature's 

 provisions for securing cross-fertilization, and the plants come under 

 the recognized Knight's law that "nature intended that a sexual inter- 

 course should take place between neighboring plants of the same 

 species." ' 



Self-sterility may also be due in some degree to imperfect pistils, 

 the cause for which must be sought in some physiological weakness 

 of the tree, such as might be brought about by the work of insects 

 or disease, or from a feeble condition following the production of a 

 phenomenally heavy crop of fruit. Or it may be due to unfavorable 

 weather conditions i)revailing at blooming time. 



Recognizing, then, the existence of self -sterility among plums, the 

 aim should be to so associate the varieties that one may supply pollen 

 for the other. No data are at hand to warrant any definite statement 

 as to what varieties are especially adapted to the fertilization of certain 

 other varieties, but it is perfectly i^lain that to be of use to each other 

 the varieties must bloom at the same time. 



The varieties now available from which to choose show a rather 

 wide range in blooming period; some bloom together, some finish 

 before others begin, and some overlap. All are much influenced by 

 the weather at the time, and this may vary greatly in different years, 

 not only in the appearance of the first flowers, but in the length of 

 the blooming period. While irregularities may occur from one season 

 to another, it is probable that the relative periods of the different 

 varieties will remain much the same. 



