10
The Evolution of Fruits.
which seedlings can hardly flourish. It is to secure the
dispersion of the seed that fruits become attractive to
birds.
In the insertion of foliar organs the spiral arrangement is
far more general and in all probability earlier than the
whorled : the multiplication of similar parts is a rudimentary
character throughout organic nature, as exemplified in the
somites of a centipede or the tail-vertebrae of Arehaeopteryx;
every probability of comparative anatomy points to the
earliest carpels as being as leaf-like as those of a pea, or of
the bladder-senna (Colutea), and to the ovules as being several
in number in each of the distinct carpellary ovarian chambers.
In other words, we have as our primitive fruit a spiral of
follicles, as in Magnolia.
That from such a starting-point such infinitely various
forms should have resulted may perhaps be partly explained
by the abundant supply of available nutriment determined
towards the ovary by the act of impregnation, as towards a
leaf or shoot by the virus of a gall-fly.
Reproductive structures being produced under influences
diametrically opposed to. those stimulating vegetative growth,
there is a general tendency to truncation of the floral axis,
the alternate phyllotaxis thus producing an arrangement of
the floral organs in whorls of five or three—an arrangement
soon inherited congenitally.
The crowding of the organs towards the centre of a
flattened floral receptacle tends to reduce the number of
carpels compared to that of the sepals, petals, and stamens;
and similarly the crowding within the ovary tends to produce
the abortion and reduction in the number of ovules. Nor is
this mechanical result disadvantageous. It allows of the
larger growth of the seed, i. e., the accumulation of a more
abundant food-supply, rendering the seedling longer inde-
pendent of the atmosphere. Most small annuals, which are
exposed to great risk of individual extermination, produce
numerous small seeds; but, as large and highly-organised
animals, such as the elephant, produce few offspring, so trees
which exist longer individually do not require many seeds in