Some
flowers on these seedlings were then crossed with pollen taken from a
distinct seedling, and other flowers were self-fertilised; two fresh
lots of seedlings being thus raised, which were the grandchildren of the
plant that had spread by stolons and formed a large clump in my garden.
These differed much in height, the crossed plants being to the
self-fertilised as 100 to 86. They differed, also, to a wonderful degree
in constitutional vigour. The crossed plants flowered first, and
produced exactly twice as many flower-stems; and they afterwards
increased by stolons to such an extent as almost to overwhelm the
self-fertilised plants.
Reviewing these five cases, we see that in four of them, the effect of a
cross between flowers on the same plant (even on offsets of the same
plant growing on separate roots, as with the Pelargonium and Origanum)
does not differ from that of the strictest self-fertilisation. Indeed,
in two of the cases the self-fertilised plants were superior to such
intercrossed plants. With Digitalis a cross between the flowers on the
same plant certainly did do some good, yet very slight compared with
that from a cross between distinct plants. On the whole the results here
arrived at, if we bear in mind that the flower-buds are to a certain
extent distinct individuals and occasionally vary independently of one
another, agree well with our general conclusion, that the advantages of
a cross depend on the progenitors of the crossed plants possessing
somewhat different constitutions, either from having been exposed to
different conditions, or to their having varied from unknown causes in a
manner which we in our ignorance are forced to speak of as spontaneous.
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