AUTHOR’S PREFACE ix 
immense amount of material, I must now and then have overlooked 
observations on the flower pollination of foreign species. But in such cases 
these will be found in the third volume. On the other hand, a comparative 
review has been given in the second volume of Ekstam’s accounts of 
flowers and their guests in Nova Zemlia, the observations of Lindman 
on floral structure and pollinating agents made in the Dovrefjeld region 
of the Scandinavian Highlands, the similar researches of Warming with 
regard both to this region and Greenland, and the works of Aurivillius 
on insect life in the high North. 
Only the most important of the very numerous descriptions given 
in Kerner’s ‘Natural History of Plants’ have been referred to in the 
second volume of this handbook, as most of them are briefly mentioned 
in Volume I. A complete purview of the very extensive material gathered 
together in the ‘Natural History of Plants’ has not been attempted, as 
Kerner’s work is very widely known. 
In describing the natural orders of plants from the point of view of 
flower pollination, the indigenous European forms are dealt with at greatest 
length ; extra-European species are referred to only occasionally, as they 
are reserved for treatment in the following volume. 
I have endeavoured in this handbook to establish generic characters in 
flower pollination, as I previously did in my work ‘Blumen und Insekten 
auf den nordfriesischen Inseln’; yet this has not been practicable in all 
cases, for the observations on some species were too imperfect. 
It was not always possible with the resources at my disposal to 
determine the authors of names of species; and as reference to the 
biologist in whose work I found a name did not always furnish the 
desired information, a few species of plants have had to remain without 
an author’s name. 
Besides observations on insect-visits recorded in works specially de- 
voted to flower pollination, there are also included records from numerous 
purely entomological works and treatises, so far as these leave no doubt 
as to the species of plant concerned’. Among these works are those 
mentioned in the bibliography (vol. i, p. 212) under the names of the 
following authors :— Alfken, André, Aurivillius, Bonnier, Cobelli, v. Dalla 
Torre, Dours, Ducke, Entleutner, Frey, Frey-Gessner, v. Fricken, Friese, 
Gerstaecker, Handlirsch, Hoffer, Holmgren, Koch, Kohl, Krieger, Leege, 
Marquard, Morawitz, Nylander, Pérez, Redtenbacher, Réssler, Saunders, 
Schenck, Schletterer, Schiner, Schmiedeknecht, Schultess - Rechberg, 
Sickmann, Smith, Thomson, and Wiistnei. 
1 Ambiguous references are neglected,—such as: ‘ Especially in som species of Centaurea and 
Sedum? An exception is made, however, in the case of Sa/ix, as experience shows that insects visit 
the various species indiscriminately. 
