POLLINATION 
25 
right for fertilizing the blossoms of another variety. Two such self-sterile 
varieties may bo planted together; if dependent on their own pollen, they 
would not set any fruit, but by the interchanging of pollen both produce. 
Comparatively few varieties are known to be absolutely self-sterile, 
but there are a great many which have a tendency towards self-sterility. 
Others are usually self-fertile. Both classes vary with external condi- 
tions. For e-xamplo, the Kieffer pear is self-fertile in the South, and self- 
sterile in the North. In some cases Nature makes self-pollination impos- 
sible by the ripening of the pollen of the blossom before the ovary is 
mature and ready to receive it. Cross-pollination makes large and most 
uniform fruit. It has been found by practical experience that some com- 
binations of pollen are especially good. Examples are: In plum: Green 
Gage with Italian Prune, Wild Goose with DeSoto; Burbank with Red 
June; in pear, Kaeffer with Garber. 
Generally speaking, any variety which is prolific, the blossoms of 
which are supplied with lots of pollen, makes a very good poUenizer if it 
comes in bloom at the same time as varieties which are weak in pollen. 
Most of the benefit comes in abundance and vigor. The pollen seldom 
has any direct effect upon the quality of the fruit. 
Such varieties as Bartlett and Clapp will produce larger and most 
uniform fruit when fertilized with some of their own pollen. 
Other Causes. A tree weakened in vitality through lack of culti- 
vation has a tendency to become self-sterile, and if it grows still weaker, 
the blossoms may fail to set fruit even with fresh pollen from another 
variety. This is very often the case, and the soil should be constantly 
enriched by a system of cover crops and manuring. On the other hand, 
a tree growing too vigorously may have blossoms, but fail to set fruit. 
However, this is seldom the case. When it occurs, it is in young orchards 
which are longer than necessary coming into bearing. The growth may 
be cheeked by allowing the orchard to remain in sod for a year. 
Bees. The importance of such insects as bees can not be too strongly 
emphasized. In many regions there are sufficient honey-bees and bumble- 
bees to produce^thorough cross-pollination, but in large orchards or 
sections where there'are^manyjorchards every grower should keep one or 
more/ stands of,' bees. 
Crown Gall and Hairy Root of the Apple. 
Trees that are not healthy are not vigorous. Care should be taken to buy 
only sound trees, free Irom Injurious Insects and diseases. The above shows 
Crown Gall and Hairy Root, which are two forms of the same disease, which 
live In the tissues oi the roots, either causing Crown Gall or peculiar bunches 
of roots, which arc enlarged and fleshy, and easily distinguished fronn the 
sound, fibrous roots. 
