The histoiogical development of fertilized ovules during fruit-set and development in
pea {Pisum sativum L. cv. Alaska) has been investigated. Killing the ovules on day 0
(anthesis) or day 1 prevented fruit-set and resulted in ovary degeneration. When the
ovules were destroyed at later stages tbe ovaries developed, though the rate of
growth of the pod was reduced significantly. Pollination in pea occurs normally the
day before anthesis, and fertilization of the egg cell 32 to 48 h later. The first divisions
of the zygote and endosperm nuclei started simultaneously (ca 48 h after pollination)
but the endosperm developed more rapidly than the embryo; the embryo sac cavity
was lined with free endosperm nuclei at the time of beginning suspensor elongation.
Extracts of endosperm and ovule coats from ovules at day 7 after anthesis showed
fruit-set activity in pea, the latter material having about 3 times more activity than the
former per ovule basis. These results indicate that fertilization of the ovule is
necessary for fruit-set in pea, and that compounds which induce fruit-set are probably
synthesized in the ovules foliowing fertiliz,ation.