THE

EFFECTS

OF

CROSS AND SELF-FERTILISATION.

CIIAITER I.

IXTRODVCTORY REMARKS.

Various menus which favour or determine the cross-fertilisation ofplants—Benefits derived from cross-fertilisation—Self-fertilisationfavourable to the propagation of the species—Brief history of thesubject—Object of the experiments, and the manner in which theywere tried—Statistical value of the measurements—The experi-ments carried on during several successive generations—Natureof the relationship of the plants in the later generations—Unifor-mity of the conditions to which the plants were subjected—Someapparent and some real causes of error—Amount of pollen em-ployed—Arrangement of the work—Importance of the conclusions.

There is weighty and abundant evidence that thetiowers of most kinds of plants are constructed so asto he occasionally or habitually cross-fertilised bypollen from another dower, produced either by thesame plant, or generally, as we shall hereafter seereason to believe, by a distinct plant. Cross-fertilisa-tion is sometimes ensured by the sexes being separated,and in a large number of cases by the pollen andstigma of the same flower being matured at differenttimes. Such plants are called dichogamous, and havebeen divided into two sub-classes: proterandrous species,

B