June, 1933] Pollination and Fruit Setting in the Apple 27 



To test the differences in anatomy of terminal and lateral flowers and the 

 effect of these on the resultant fruit crop, a number of trees have been used 

 experimentally. Terminal flowers were tagged and the two types of fruit 

 developed were observed at harvest time. In a future publication a compari- 

 son of the rate of growth in terminal and lateral flowers of the cluster will 

 be presented. 



Table VI shows data obtained in preliminary experiments to determine 

 quantitatively difference between terminal and lateral fruits on the cluster. 

 The trees concerned had all terminal flowers tagged while they were open. 

 At harvest time the tags still remained on the stems of the terminal fruits 

 which could easily be separated out and compared with the lateral ones on 

 the same tree. In all cases the terminal flowers produced larger fruits. In 

 addition to this important feature terminally developed fruits have better 

 form as indicated by the greater percentage of lopsided fruits among the 

 laterals. Aside from the better position of the terminal fruits to receive 

 foods and water from the tree, two explanations of this better form and 

 size are possible from a glance at the data. An increase of approximately 

 20 percent in weight is accompanied by an increase of two seeds per fruit 

 in the terminals over the laterals. The shorter and thicker stems of the 

 terminal fruits may also aid in causing a better development of the fruits. 



In these trees terminal and lateral fruits were rarely matured on the 

 same clusters, so that difference in size and shape could be considered as 

 due purely to anatomical and physiological differences between the terminal 

 and lateral flowers. That there is less difference in diameter than in length 

 between fruits from terminal and lateral flowers can be determined from 

 Table VI. It may be seen that the ratio between length of terminals and 

 laterals is greater than between the diameters of the two. 



VI. Pollination and Orchard Planting 

 and Management 



For satisfactory pollination, it is evident, first of all, that the apple must 

 be pollinated by the apple, the pear by the pear, etc. This does not mean . 

 that fruits of different genera and in many cases of different species cannot 

 possibly be crossed, but such crosses are rare and usually only result, when 

 they are possible, after hand pollination. 



Coincidence of Blooming Periods of Varieties: 



It would be unreasonable to interplant an orchard of one variety with 

 trees of another variety and expect cross pollination to occur if the two 

 varieties did not have at least a few flowers open at the same time. This is 

 evident because we know that the pollen is shed and is available to insects 

 only after the flowers have fully opened. 



Even though the flowers of an early blooming sort may in some years 

 remain on the tree until the opening of some of the flowers of a later vari- 

 ety for which pollination is desired, in other years, especially when unusu- 

 ally warm weather prevails at blossom time, the flowers of the early variety 

 may be shed before the later one opens its buds. The pistils are in a recep- 

 tive condition as soon as or even just before the buds open. The bumble- 

 bee is the only insect able to push the petals of unopened buds apart, and it 

 would only be such insects that could possibly pollinate unopened flowers. 



