speculations on the origin of species, that
crossing played an important part in keeping specific forms constant. I
attended to the subject more or less during every subsequent summer; and
my interest in it was greatly enhanced by having procured and read
in November 1841, through the advice of Robert Brown, a copy of C.K.
Sprengel's wonderful book, 'Das entdeckte Geheimniss der Natur.' For
some years before 1862 I had specially attended to the fertilisation
of our British orchids; and it seemed to me the best plan to prepare as
complete a treatise on this group of plants as well as I could, rather
than to utilise the great mass of matter which I had slowly collected
with respect to other plants.

My resolve proved a wise one; for since the appearance of my book, a
surprising number of papers and separate works on the fertilisation of
all kinds of flowers have appeared: and these are far better done than
I could possibly have effected. The merits of poor old Sprengel, so long
overlooked, are now fully recognised many years after his death.

During the same year I published in the 'Journal of the Linnean Society'
a paper "On the Two Forms, or Dimorphic Condition of Primula,"
and during the next five years, five other papers on dimorphic and
trimorphic plants. I do not think anything in my scientific life has
given me so much satisfaction as making out the meaning of the structure
of these plants. I had noticed in 1838 or 1839 the dimorphism of Linum
flavum, and had at first thought that it was merely a case of unmeaning
variability. But on examining the common species of Primula I found that
the two forms were much too regular and constant to be thus viewed. I
therefore became almost convinced that the common cowslip and primrose
were on the high road to become dioecious;--that the short pistil in the
one form, and the short stamens in the other form were tending towards
abortion. The plants were therefore subjected under this point of view
to trial; but as soon as the flowers with short pistils fertilised with
pollen from the short stamens, were found to yield more seeds than any
other of the four possible unions, the abortion-theory was knocked on
the head. After some additional experiment, it became evident that the
two forms, though both were perfect hermaphrodites, bore almost the same
relation to one another as do the two sexes of an ordinary animal. With
Lythrum we have the still more wonderful case of three form