ed an intense and prolonged controversy, and incited emulous
investigation by the botanists of his time. Though a few of the more
advanced of his followers, among them Andrew Knight (1799), Koehlreuter
(1811), Herbert (1837), Gaertner (1844), clearly recognized the principle
and foreshadowed the later theory of cross-fertilization, it was not
until the inspired insight of Darwin, as voiced in his "Origin of
Species," contemplated these strange facts and inconsistencies of
Sprengel that their full significance and actual value were discovered
and demonstrated, and his remarkable book, forgotten for seventy years,
at last appreciated for its true worth. Alas for the irony of fate!
Under Darwin's interpretation the very "defects" which had rendered
Sprengel's work a failure now became the absolute witness of a deeper
truth which Sprengel had failed to discern. One more short step and he
had reached the goal. But this last step was reserved for the later
seer. He took the fatal double problem of Sprengel--as shown at E and F,
to express the consummation pictorially--and by the simple drawing of a
line, as it were, as indicated between G and H, instantly reconciled all
the previous perplexities and inconsistencies, thus demonstrating the
fundamental plan involved in floral construction to be not merely
"_insect_ fertilization," the fatal postulate assumed by Sprengel, but
_cross_-fertilization--a fact which, singularly enough, the latter's
own pages proved without his suspicion.

Thus we see the four successive steps in progressive knowledge, from
Grew in 1682, Linnaeus, 1735, Sprengel, 1787, to Darwin, 1857-1858, and
realize with astonishment that it has taken over one hundred and
seventy-five years for humanity to learn this apparently simple lesson,
which for untold centuries has been noised abroad on the murmuring wings
of every bee in the meadow, and demonstrated in almost every flower.

This infinite field now open before him, Darwin began his
investigations, and the whole world knows his triumphs. He has been
followed by a host of disciples, to whom his books have come as an
inspiration and ennobling impulse. Hildebrand, Delpino, Axell, Lubbock,
and, latest and perhaps most conspicuous, Hermann Mueller, to whom the
American reader is especially referred. "The Fertilization of Flowers,"
by this most scholarly and indefatigable chronicler, presents the most
complete compendium and bibliography of the literature on the s