Immediately
after fertilization the pollen-receptive center of the female
flower, the pistal, turns black and shrivels up; and the
ovaries enlarge. Notice the black poison canals in the petals,
and in the large fruit at the right:
As the fruits
enlarge the petals shrivel. There is a poison canal at the
base of each grove, which will later become black again. The
fruit is borne on irregularly branched stalks from the sides
of stems; these characteristics, plus whitish ripe fruit and
subulate filaments (see flowers) are the
characteristics that define poison-oaks genus, Toxicodendron:
The skin,
peel, or husk of mature poison-oak fruits is stiff and
crumbly; I imagine that birds remove it by rolling the fruit
in their mouths before swallowing, or pulverize the husks in
their gizzards. (Birds do not chew.) In any case, the husks
cover the poison canals (the black lines), and the easily
digested and presumably tasty pulp (the white part).