22 INTRODUCTION 
arrangements of flowers considered in relation to actual insect visits, that crossing 
is absolutely the more advantageous mode of fertilization. If, on the one hand, 
the experimental method has the advantage of being directly demonstrative, there” 
is, on the other hand, a much larger amount of indirect evidence adducible from 
the arrangements for pollination. It is, perhaps, hardly more difficult to obtain 
indirect evidence from a few hundred flowers than to make direct experiments 
on a few. If by itself, such evidence would scarcely satisfy us, yet it brings 
complete conviction when considered along with the results of the Darwinian 
experiments, and takes us even a step further than those experiments. From 
Darwin’s experiments, which lasted eleven years, it is not proved, and perhaps 
it would not be proved if the experiments lasted a hundred years, whether the 
capacity of certain flowers to reproduce by spontaneous self-pollination is limited 
or unlimited. From the floral arrangements, on the other hand, we can conclude 
that this capacity must have its limit. For, were it unlimited, cleistogamous flowers. 
would be the most advantageous, and many plants would necessarily have come 
to possess such flowers only. As a matter of fact, however, not a single plant 
is known which reproduces itself exclusively by spontaneous self-fertilization. The 
investigation of pollination arrangements in connection with actual insect-visits 
therefore furnishes evidence that is very convincing, even though of secondary 
nature. It constitutes a no less essential support of the floral theory than the 
experimental proof that, as a matter of fact, more vigorous offspring result from 
crossing than from self-fertilization.’ 
Hermann Miiller’s works stimulated many botanists in the most marked way, 
and a vigour never before manifest became apparent in the field of Flower Pollination. 
In addition to the older specialists, Darwin, Delpino, Hildebrand, Hermann Miiller, 
and his brother, who was no less enthusiastic for this science, a number of younger 
investigators began to apply themselves to this branch, so that a division of labour 
resulted, and the investigations undertaken in various districts were directed partly 
to the extension of the various sections of Flower Pollination, partly to an investigation 
of floral arrangements, and the discovering of the visitors of flowers. Our know- 
ledge of nectaries’ was extended in Germany by the works of W. J. Behrens; in 
France by Gaston Bonnier; in North America by Trealease (all 1879). Investigations 
on stamens were published by Chatin (France), Askenasy, H. Fischer, Oetker 
(Germany), Bennett (England); on stigmas by J. Reinke, Behrens (Germany), 
Capus (France); on the processes of fertilization by Dalmer, Strasburger, Elfving, 
Treub, Juranyi, Goroschankin, Guignard; on the distribution of sexes by Asa 
Gray, E. Warming, Hackel, Breitenbach, Magnus, Potonié, Errera and Gevaert, 
F. Ludwig, Solms-Laubach; on heterostyly by Breitenbach, Kny, Kéhne, W. Burck, 
Urban, Bailey, Clarke, Meehan, Ernst, Bessey, Battandier, Todd, Knoblauch, Pirotta, 
Wilson; on cleistogamy by Ascherson, Potonié, Batalin, Ludwig, Trealease, Heckel, 
Pringle, Asa Gray, Godron, Hackel, Meehan, Coulter, Graebner, Schréter, Battan- 
dier, G. M. Thompson, Grisebach, Drude, Kearney, Kéhne, Solms-Laubach, Burck ; 
on pseudo- and hemi-cleistogamy by Fitzgerald, Moore, Reichenbach fil., Freyhold, 
1 Partly taken from Loew :—‘Einfiihrung in die Bliitenbiologie,’ pp. 291 et seq., and ‘ Bliiten- 
biologische Floristik,’ pp. 172-5. 
a 
