149 



removed. The author, Mr. W. H. Alder- 

 man, thinks the explanation may be that 

 the advantage is due to the fact that the 

 blossoms are protected from superabun- 

 dant pollination from their own pollen. 

 Probably self-pollination frequently occurs 

 naturally in such cases before the artificial 

 cross-pollination is brought about; foreign 

 pollen tubes must then actively compete 

 with many tubes from its own pollen, with 

 the result that the chances of cross-ferti- 

 lisation are lessened; something of this 

 sort has been proved as the result of 

 further trials. Two methods of emascula- 

 tion are employed : in (A) the petals of 

 the unopened flower are quickly removed 

 by one jerk with the thumb and forefinger, 

 and then with one or two movements of 

 a fine toothed comb the anthers are raked 

 out without injury to the pistil; or (B) the 

 flower is grasped firmly and a quick snap 

 with the finger-nail just under the edge 

 of the calyx removes calyx, corolla, and 

 stamens, leaving pistil and receptacle 

 clean and bare. For some varieties one 

 method is the better adapted, for 

 other varieties the other method. 



Cross-pollination as a rule brings about 

 an increase in number of seeds and in the 

 weight of the fruit; by experiment with 

 Home Beauty, York Imperial and 

 Wagener there are found to be two to six 

 times as many seeds in crossed fruits as 

 in the selfed ones. This is found to be a 

 larger proportion than works out in prac- 

 tice in the orchard, which may be due to 

 the fact that trees which set fruit with 

 their own pollen almost invariably set 

 fruit sparsely and consequently are able 

 to grow these to a larger size than they 

 otherwise would be able to do. 



200 tests were made to ascertain 

 whether there was anything toxic which 

 prevented pollen germinating in stigmatic 

 extract from their own pistil stigmas, but 



germination of all the varieties seemed 

 equally good whether the medium was ex- 

 tracted from their own stigmas, or from 

 other varieties. Good germination of 

 apple pollen was founci to take place even 

 on the stigmatic extract from cucumber, 

 tomato and geranium blossoms. 



In 1915 an orchard of Rome Beauty that 

 had been bearing only moderate crops, 

 was used for a practical test of the value 

 OF CROSS-POLLINATION. Six hives of bees 

 were placed in a section of the orchard 

 and sixteen trees in a block surrounding 

 them were placed under observation. 

 Large blooming branches of other 

 varieties were brought in and placed up- 

 right in pails of water suspended from 

 trees. The bees worked this block of trees 

 thoroughly, and presumably made a great 

 number of cross-pollinations. Another 

 block of 15 trees at some distance was 

 used as a check. The amount of blossom 

 upon each block was about equal, being 

 81 per cent, in the bee plot and 83 per 

 cent, in the check. Sample counts of 

 about 9,000 blossoms showed a set of 12.6 

 per cent, in the bee plot, and 7.8 per cent, 

 in the check. In another part of the 

 orchard, where a Ben Davis tree had been 

 planted by a mistake the set of fruit was 

 20 per cent, on adjacent trees. The sixteen 

 trees fertilised by the bees produced 174 

 bushels, and the check block 83 bushels. 

 These tests and those of 1916 indicate 

 clearly the value of bees in an orchard. 

 The trees in the bee plot were unquestion- 

 ably more thoroughly self-fertilized than 

 in the rest of the orchard, and this fact 

 itself would have probably produced some 

 gain, but it seems clear that this could 

 not adequately explain a percentage of 

 set double that of the normal, hence we 

 believe the greatest gain was secured by 

 reason of the cross pollination that must 

 have taken place. 



