28 INTRODUCTION 
observations. On the other hand, processes of pollination that were not 
described by Miiler, and plants investigated by later observers, are treated at 
somewhat greater length. Occasionally, Loew goes back to older publications 
when this seems necessary for the completion of his accounts. Owing to the 
exigencies of space, lists of visitors had to be excluded, but in the case of 
certain plants at least the chief groups of the flower visitors are given, together 
with an enumeration of species. Loew’s ‘Bliitenbiologische Floristik’ has been 
an indispensable work of reference for me during the production of this work, 
and many facts have been taken from it. 
SECOND SECTION 
PRESENT STANDPOINT OF FLOWER POLLINATION 
I. Survey of the Modes of Pollination and of the 
Distribution of the Sexes. 
The following chief kinds of pollination and fertilization are known to us at 
the present time :— 
(I) Autogamy (Delpino), or Self-pollination: the pollen reaches the stigma 
of the same flower. Autogamy is therefore only possible in hermaphrodite flowers. 
When effective the result is Autocarpy, or Self-fertility; if not effective, Self- 
sterility. 
(a) Direct Autogamy (Spontaneous Self-pollination) depends upon the relative 
positions of stigma and anthers, without reference to external agency. 
If it is effective the result is Direct Autocarpy. 
(6) Indirect Autogamy (Self-pollination in the narrower sense) is brought about 
by external agency. If effective the result is Indirect Autocarpy. 
(II) Allogamy (Kerner), or Cross-pollination. The pollen reaches the stigma 
of another flower. If effective the result is Allocarpy; if non-effective there is 
Adynamandry. 
(a) Gettonogamy (Kerner), or Pollination by a neighbour, occurs between 
flowers of the same plant. If it is effective the result is Geitonocarpy. 
(2) Xenogamy (Kerner), or Crossing, occurs between flowers of different plants 
of the same species. If effective the result is Xenocarpy. 
(III) Hybridization occurs between flowers of different species. If effective the 
result is Hybridocarpy. 
The most important known ways in which the sexes are distributed, as well 
as the various possibilities of pollination conditioned by the arrangement of stamens 
and carpels, may be summarized as follows !:— 
Cf. Kirchner, ‘ Flora von Stuttgart’ (pp. 38-40). 
