646 EXPERIMENT STATION RECORD. [Vol. 43 



fourths of those varieties pollinated with pollen of other varieties set fruit 

 satisfactorily. Hence, it is concluded that every apple j^rower should provide 

 suitable varieties for pollinators if large, dependable crops are to be secured. 

 The results secured in this investigation indicate that it is necessary to test 

 a variety for cross compatibility before any conclusion can be drawn for the 

 variety. 



When cross-pollination is effected, the size, color, and quality of the fruit 

 remain practically the same as the standard for the mother parent. The 

 number of good seeds in the crossed apples is greater than in tliose which are 

 selfed. External causes of self-sterility, such as weather, si)raying, inspects, 

 and disease, are somewhat within the control of the grower. The chief in- 

 ternal cause of sterility is the slowness of growth of the pollen tube in the 

 selfed style as against that in the crossed style. 



Coniparisou of fall, winter, and spring' pruning of apple trees in Minne- 

 sota, W. G. Briekley {Proe. Amer. Soc. llort. tScL, 16 {li)19), pp. 102-10.^).— A 

 contribution from the Minnesota Experiment Station, giving the results of 

 pruning experiments conducted during the seasons of 1913-17, inclusive, and 

 confirming a pi'evious report on this work to the effect that apple trees in 

 Minnesota may be pruned safely at convenient times during the fall, winter, 

 and spring (E. S. R., 39, p. 347). 



The maturity of shoots and the healing of wounds, as well as the amount of 

 winter injury, was practically the same for all pruning seasons tested. Like- 

 wise there was no detrimental effect upon growth chargeable to pruning in the 

 late fall or in the winter under normal conditions. 



Some influences of thinning, pollination, and fruit spur growth on the 

 yearly performance record of fruit spurs and on the size of fruit produced, 

 E. C. AucHTEK {Froc. Amer. Soc. Hort. ScL, 16 {1919), pp. 118-131).— This bul- 

 letin presents results secured since 1916 of thinning experiments with apples 

 started at the West Virginia Experiment Station in 1912 (E. S. R., 37, p. 448), 

 and summarizes the results of the investigations to date. 



It is concluded that fruit thinning does not affect the annual bearing of 

 apple trees. In cases where the trees are bearing a good crop of fruit, thinning 

 increases the size of the individual apples and the total quantity of market- 

 able fruit for the current season. This influence is lessened or lost altogether 

 when trees are bearing light crops. 



Spurs on certain varieties of apples bloom more regularly than those of 

 other varieties, but do not necessarily bear fruit more regularly. Generally 

 speaking, spurs which set fruit one year do not blossom the next year. Spurs 

 which blossom one year but do not set fruit may or may not blossom the next 

 year. Spurs which blossom two years in succession make a gi'eater yearly 

 growth, have more leaves, and a greater total leaf area in the year preceding 

 the second successive blooming year. Thus it appears that growth and vigor 

 to a certain degree do not oppose but rather encourage fruitfulness. The re- 

 sults indicate that a variety is an annual bearer because either a certain per- 

 centage of the total spurs on such a variety does not bloom in the heavy crop 

 year and, therefore, blooms and sets fruit the next year, or if all the spurs do 

 bloom a certain percentage of the spurs does not set and thus more readily 

 blooms and sets the next year. It ap))ears that a large proportion of the spurs 

 on tlie biennial bearers not only bloom but also set fruit in the crop year. 

 Such spurs do not readily bloom the next year. 



Certain varieties which produce fruit yearly form fruit buds terminally and 

 laterally on one-year-old growths to such an extent that the production of 

 fruit from these sources is often enough to class a variety as an annual bearer 

 without reference to its fruit spurs. From the results thus far secured, the 



