8
II. The Evolution of Fruits.
By Professor G. S. Boulger, F.L.S., F.G.S.
[Abstract of Discourse delivered viva voce, February 2Gth, 1881.]
Syllabus.—The Descent Theory.—Definition of the word "Fruit."—
Origin of fruits.—Marginal placentation.—Object of fruits.—Possible
cause of the variability of the fruit.—Generalizations as to the course of
variation in fruits.—Ontogeny of the fruit.—The phylogenetic importance
of the fruit, and the results of the study of the fruit on the phylogenetic
classification of flowering plants.
One of the strongest confirmations of the Descent Theory
is its vital energy. It is not only consistent with hosts of
ever-accumulating facts in every department of Biology, but
it is constantly suggesting new lines of inquiry to which it
forms the only key. Thus, though in tracing the evolution
of the numerous kinds of fruit from the simplest and pre-
sumably earliest forms, it is necessary to assume this theory
as a working hypothesis, not the least important result of
the investigation will be the accumulation of much evidence
that by its self-consistence tends strongly to show that the
hypothesis truly represents the facts of Nature.
Affixing the definite meaning to the word "fruit" of "the
whole of the gynaecium which ripens in consequence of
fertilisation, together with all surrounding accrescent or
succulent parts, originating from a single flower,"—a
definition free from many of the objections which attach to
Sachs' use of the word for each apocarpous carpel,—we find
nothing really analogous to a fruit among Cryptogamic
plants. The highest degree to which secondary sexual
organs are developed in these groups only amounts to the
formation of a seed. It is among the Gymnosperms that we
have the nearest approach to the origin of the fruit.
Without concerning ourselves with the cognate but distinct