The wild olive Oleaster is said to have been the original form, called
by Linnaeus _Olea europaea sylvestris_, later by De Candolle _Olea
europaea oleaster_ and the cultivated form _Olea europaea sativa_. The
reason for this belief is said to be the _oleaster_ seeds reproduce
trees true to type, whereas the seeds of _sativa_ produce trees having
the characteristics of _oleaster_ but, though _oleaster_ under
cultivation becomes modified in various ways, it does not produce fruit
like _sativa_. Whichever form was the original, the subjection to
cultivation for over 4,000 years, under the varying conditions of soil,
climate, and methods of cultivation, has produced many varieties. Many
of these doubtless are the result of accidental modifications, more or
less fixed by successive cultivations. At the present time there are
certain well-defined varieties which are cultivated, and of which the
characteristics are well known, so that varieties may be selected
according to the purpose desired, whether for the preservation of the
fruit green, half ripe, or ripe, or for extraction of oil.
Of the large number of varieties introduced into California, Wickson
reports analyses made by the State university on 57 varieties. Of these
only a comparatively few were retained as worthy of cultivation, chief
among these being the Mission olive, the one planted originally in
California in the old mission gardens. Wickson states there are several
sub-varieties of this form.