26 N. H. Agricultural Experiment Station [Bulletin 274 



Next to Baldwin, Cortland and Oldenburg failed to show themselves as 

 satisfactory pollenizers for Gravenstein. Mcintosh, Red Astrachan, Wag- 

 ener and Early Harvest did not produce a high set in 1930, yet owing to the 

 heavy blooming habit of Gravenstein, 30 per cent would ordinarily be 

 sufficient. 



The foregoing results of pollination with Mcintosh, Cortland, Delicious 

 and Gravenstein emphasize the fact that these varieties are not only self- 

 unfruitful but may fail to be poUenized satisfactorily by some other varie- 

 ties. Self -unfruitful varieties used as pollenizers may not bear fruit unless 

 these facts are taken into consideration. 



Relation of Pollen Viability to Set of Fruit in Cross Pollination: 



Poor set when certain varieties are used as pollenizers is probably due to 

 a large extent to natural abnormality of the pollen of these varieties. These 

 abnormalities may vary in different seasons. 



Many investigators have found in artificial germination tests that Bald- 

 win pollen germinates very poorly. Many of the pollen grains are imperfect 

 in their development. Gravenstein also usually exhibits rather poor germi- 

 nating power, but in this respect is less constant throughout a period of 

 years than Baldwin. These facts partially explain why the low sets of fruit 

 indicated in Table I are obtained when these varieties are used as pollen- 

 izers for Mcintosh. It is also known that these varieties dift'er from 

 Mcintosh in the genetical make-up of the tissues. 



Delicious is just the opposite. It produces well- formed pollen grains 

 which germinate from 95 to 100 per cent on artificial media. It is one of 

 the most satisfactory all-round pollenizers in existence. 



Effect of Position of the Flower in the Cluster on Set of Fruit: 



That all of the flowers in the cluster do not open at the same time is well 

 known. The first to open is the central or terminal flower in the cluster. 

 The latest to open are those at the base of the cluster. 



Generally the first flowers to be pollinated in the cluster will remain on 

 the tree through the June drop. Under most Xew Hampshire conditions, 

 this will be the terminal flower. Yet if weather conditions are unsatisfac- 

 tory for bee flight and consequently for pollination when the terminal 

 flowers are receptive, the latter may fall oft" during or before the June drop. 

 Those blossoming later, if they open under more favorable weather condi- 

 tions, will then produce the fruit. With some varieties the first flowers to 

 open may be injured by frost occasionally because of their advanced devel- 

 opment, and again the later opening buds will be the ones to develop fruit. 



\\'hcthcr the crop came mainly from terminal or from lateral flowers of 

 the cluster can easily be determined with Mcintosh. Fruits developing from 

 lateral flowers are flatter in shape and have usually much longer and more 

 slender stems than those from terminal flowers of the spur. Fruits from 

 terminal flowers are usually decidedly more attractive in appearance, and 

 have better form and size due partly to the greater seed development. The 

 position of these flowers in the cluster predetermines shape and other differ- 

 ences. Even in the dormant winter buds the superior size of the terminal 

 flower and its larger stem diameter may be seen. They are in a better posi- 

 tion to receive food, minerals and water from the tree. 



