ause apparently lies in an innate sexual incompatibility
of the pair which are matched. Several instances have been communicated
to me by Mr. W. C. Spooner (well known for his essay on
Cross-breeding), by Mr. Eyton of Eyton, by Mr. Wicksted and othe
breeders, and especially by Mr. Waring of Chelsfield, in relation to
horses, cattle, pigs, foxhounds, other dogs, and pigeons.[395] In these
cases, females, which either previously or subsequently were proved to
be fertile, failed to breed with certain males, with whom it was
particularly desired to match them. A change in the constitution of the
female may sometimes have occurred before she was put to the second
male; but in other cases this explanation is hardly tenable, for a
female, known not to be barren, has been unsuccessfully paired seven or
eight times with the same male likewise known to be perfectly fertile.
With cart-mares, which sometimes will not breed with stallions of pure
blood, but subsequently have bred with cart-stallions, Mr. Spooner is
inclined to attribute the failure to the lesser sexual power of the
race-horse. But I have heard from the greatest breeder of race-horses
at the present day, through Mr. Waring, that "it frequently occurs with
a mare to be put several times during one or two seasons to a
particular stallion of acknowledged power, and yet prove barren; the
mare afterwards breeding at once with some other horse." These facts
are worth recording, as they show, like so many previous facts, on what
slight constitutional differences the fertility of an animal often
depends.

{163}

_Sterility of Plants from changed Conditions of Life, and from other
causes._

In the vegetable kingdom cases of sterility frequently occur, analogous
with those previously given in the animal kingdom. But the subject is
obscured by several circumstances, presently to be discussed, namely, the
contabescence of the anthers, as Gaertner has named a certain
affection--monstrosities--doubleness of the flower--much-enlarged
fruit--and long-continued or excessive propagation by buds.

It is notorious that many plants in our gardens and hot-houses, though
preserved in the most perfect health, rarely or never produce seed. I
do not allude to plants which run to leaves, from being kept too damp,
or too warm, or too much manured; for these do not produce the
repr