| → cases 1859 1860 1861 1866 1869 |
| classes of cases 1872 |
|
| → their own pollen. 1859 1860 1861 1866 |
| pollen from the same plant. 1869 1872 |
|
|
in other cases species of the same genus will not take on each other. The pear can be grafted far more readily on the quince, which is ranked as a
genus, than on the apple, which is a member of the same genus. Even different varieties of the pear take with different degrees of facility on the quince; so do different varieties of the apricot and peach on certain varieties of the plum. |
|
| As Gärtner found that there was sometimes an innate difference in different
individuals
the same two species in crossing; so
believes this to be the case with different individuals of the same two species in being grafted together. As in reciprocal crosses, the facility of effecting an union is often very far from equal, so it sometimes is in grafting; the common gooseberry, for instance, cannot be grafted on the currant, whereas the currant will take, though with difficulty, on the gooseberry. |
|
| We have seen that the sterility of hybrids, which have their reproductive organs in an imperfect condition, is a
different case from the difficulty of uniting two pure species, which have their reproductive organs perfect; yet these two distinct
→cases
run to a
extent parallel. Something analogous occurs in grafting; for Thouin found that three species of Robinia, which seeded freely on their own roots, and which could be grafted with no great difficulty on
species, when thus grafted were rendered barren. On the other hand, certain species of Sorbus, when grafted on other
yielded twice as much fruit as when on their own roots. We are reminded by this latter fact of the extraordinary
of Hippeastrum,
&c., which
much more freely when fertilised with the pollen of
species, than when
with
→their own pollen.
|
