EFFECTS OF CROSSING FLOWERS ON THE SAME PLANT.
In the discussion on the results of a cross with a fresh stock, given
under Table 7/C in the last chapter, it was shown that the mere act of
crossing by itself does no good; but that the advantages thus derived
depend on the plants which are crossed, either consisting of distinct
varieties which will almost certainly differ somewhat in constitution,
or on the progenitors of the plants which are crossed, though identical
in every external character, having been subjected to somewhat different
conditions and having thus acquired some slight difference in
constitution. All the flowers produced by the same plant have been
developed from the same seed; those which expand at the same time have
been exposed to exactly the same climatic influences; and the stems have
all been nourished by the same roots. Therefore in accordance with the
conclusion just referred to, no good ought to result from crossing
flowers on the same plant. (8/1. It is, however, possible that the
stamens which differ in length or construction in the same flower may
produce pollen differing in nature, and in this manner a cross might be
made effective between the several flowers on the same plant. Mr. Macnab
states in a communication to M. Verlot 'La Production des Varietes' 1865
page 42, that seedlings raised from the shorter and longer stamens of
rhododendron differ in character; but the shorter stamens apparently are
becoming rudimentary, and the seedlings are dwarfs, so that the result
may be simply due to a want of fertilising power in the pollen, as in
the case of the dwarfed plants of Mirabilis raised by Naudin by the use
of too few pollen-grains.
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