Vill AUTHOR’S PREFACE 
Boeken, Verhandlingen,enz. omtrent de bevruchting der Bloemen,van 1883 tot 
1889 verschenen’ (Bot. Jaarb. Dodonaea, Ghent, ii, 1890, pp. 195-254); and 
lastly, the ‘ Litteraturverzeichniss (1883-93)’ in Loew’s ‘ Bliitenbiologische 
Floristik’ (Stuttgart, 1894, pp. 4-18). I have supplemented these notices 
of the literature especially by working through the references published 
by v. Dalla Torre in Just’s ‘Botanischer Jahresbericht’ from 1883 to 1895; 
and placed at my disposal by the author, and also the ‘ Neue Litteratur’ 
in the ‘Botanisches Centralblatt’ from 1880 till October 1, 1897. An 
appendix gives the works on flower pollination that have appeared during 
the printing of the first volume, up to April, 1898. Here also are named 
a few of the oldest works on the sexuality and the fertilization of flowers, 
which I had at first overlooked, as well as the literature on perception 
of form and colour, and on the olfactory and visual powers of insects, 
mostly from H. J. Kolbe’s ‘Einfiihrung in die Kenntnis der Insekten’ 
(Berlin, 1893). The bibliography as here presented should be moderately 
complete, but I cannot in every case vouch that the titles are absolutely 
correct, as the original works were not always available, and some of 
the sources on which I had to depend contain numerous printers’ errors. 
The works that appeared during the preparation and the printing of 
this handbook have been, as I have already said, taken into consideration 
as far as possible. The notices which J. Behrens has published on 
Kolreuter (Verh. Natw. Ver., Karlsruhe, 1894), and the important investiga- 
tions of F. Plateau which have been published under the title ‘Comment 
les fleurs attirent les insectes’ (Bul. Acad. roy., Bruxelles, 1895-7), are 
discussed in an appendix to the introduction. 
The second volume contains descriptions of the structure of flowers, 
and notices of the flower visitors hitherto observed in Europe and in the 
Arctic regions, and of their relations with the flowers they visit, following 
closely the accounts of the observers who first described the facts. I have, 
in particular, left unaltered, so far as possible, Hermann Miiller’s descrip- 
tions of flowers, as an account by this investigator cannot be safely 
modified: I have, however, usually made slight abbreviations. While 
descriptions of the structure of flowers belonging to indigenous European 
species have generally been retained intact, and their visitors given as 
fully as possible, I have only briefly indicated observations made in 
Europe on cultivated but non-indigenous plants. A fuller description 
will be given of these in the third volume of this work, but they could 
not be altogether omitted in the second, as it was impossible to distinguish 
sharply between indigenous, acclimatized, and cultivated species. I have, 
therefore, given short accounts of all observations made in Europe on 
plants that are not indigenous. On the other hand, I have left unnoticed 
all investigations which, though described in European periodicals, refer 
to extra-European regions. It is obvious that in dealing with such an 
