GEITONOGAMY 41 
III. Geitonogamy. 
Kerner, in his paper ‘Die Schutzmittel der Bliite, was the first to distinguish 
between Geitonogamy and Xenogamy. According to the few experiments of Darwin 
(‘The Effects of Cross- and Self-fertilisation’) and of Hildebrand (‘Geschlechter- 
verteilung,’ pp. 67, 68) it appears, as was to be expected, to be less advantageous 
for the plant than Xenogamy, but considerably more advantageous than Autogamy. 
Geitonogamy is brought about not only by atmospheric currents and the agency of 
insects, but also by mature stigmas coming into contact with the pollen-covered anthers 
of neighbouring flowers, or by the fall of pollen. Kerner gives a full account of these 
two latter kinds of Geitonogamy in his ‘ Nat. Hist. Pl.’ (Eng. Ed. 1, II, pp. 318-31). 
According to this investigator the significance of crowded inflorescences (Com- 
positae, Umbelliferae, &c.), lies chiefly in the crossing that results between neigh- 
Fic. 2. Getionogamy with adhesive pollen (after Kerner). (1) Crossing of branches of the styles of 
adjacent florets in the capitulum of Eupatorium cannabinum. (2) Longitudinal section through the 
upper parts of a young floret of Eupatorium: the two branches of the style lie parallel to one another, 
enclosed in the anther-cylinder, which is again surrounded by the corolla-tube. (3) Umbellule of Chaero- 
phyllum aromaticum: the true hermaphrodite florets are open, the pseudo-hermaphrodite pollen-florets 
still closed. (4) The same umbellule: the true hermaphrodite florets are now without stamens, the pseudo- 
hermaphrodite florets are open, pollen is dropping from the anthers of the latter upon the stigmas of the 
former. 
bouring flowers of the same plant. In numerous Compositae belonging to the 
group Liguliflorae, the spreading branches of the stigmas of adjacent florets intertwine 
at the end of the period of maturity, so that pollen entangled in the hairs of the 
style-branches comes into contact with the papillated stigmatic surfaces of the neigh- 
bouring florets. Geitonogamy is also favoured by the fact that the capitula close 
