New York AGRICULTURAL EXPERIMENT S?rATION. 647 
pollen, yet they are quite generally valued as amateur varieties, 
and some of them are occasionally planted in commercial 
vineyards. 
In these investigations with grapes it has been shown that 
although a pistil may be plentifully supplied with pollen from its 
own blossom, yet in self-sterile varieties no fruit is developed as 
a result of such pollination. In other species of plants similar 
instances have long been known. In such cases unfruitfulness 
is not due to a lack of pollen, but toa lack of the right kind of 
pollen. In many observed instances, when the pistils of self- 
sterile plants are supplied with pollen from some other variety of 
the same species, or even of some nearly related species, fruit is 
produced. — 
Another interesting fact is that the pollen which is power- 
less to incite fruitfulness on flowers of its own variety may 
be able to fertilize the blossoms of some other variety. I have 
had currants develop fruit when the pistil was supplied only 
with gorseberry pollen and vice versa, and pears when supplied 
only with apple pollen; others have reported that peach blossoms 
set fruit when supplied only with cherry pollen. These may be 
considered rather extreme cases, and in such instances the result- 
ing fruits are apt to be seedless. More nearly related species, as, 
for example, the different species of grapes or the different 
species of gooseberries, produce seeds quite readily when fer- 
tilized by each other in this way. 
Evidently the fruitfulness of a self-sterile variety may be 
accounted for by the proximity of a supply of congenial pollen, 
even though it be produced by a plant not of the same, but of 
some nearly related species, so that, while the production of fruit 
depends on a supply of congenial pollen, that supply does not 
always come from blossoms of its own variety, but may come 
from other varieties or even from other species. 
From what has been said it ought not to be inferred that in all 
instances where trees are unfruitful when standing alone the 
difficulty is due to the lack of congenial pollen for fertilizing 
their blossoms. It would be easy, for example, to show that 
many varieties of fruits are less productive when standing alone 
than when mingled with other varieties in a well-cultivated 
