Some of the cereals are, to a certain extent, self-propagating in the soil and climate of California. "VOLUNTEER crops are grown from the seed which falls out in harvesting. Barley has been known to volunteer five crops in succession."--Prayer-Frowd, Six Months in California, p. 189.] In fact, the cases are rare where the identity of a wild with a domesticated plant is considered by the best authorities as conclusively established, and we are warranted in affirming of but few of the latter, as a historically known or experimentally proved fact, that they ever did exist, or could exist, independently of man. [Footnote: This remark is much less applicable to fruit trees than to garden vegetables and the cerealia. The wild orange of Florida, though once considered indigenous, is now generally thought by botanists to be descended from the European orange introduced by the early colonists. On the wild apple trees of Massachusetts see an interesting chapter in Thoreau, Excursions. The fig and the olive are found growing wild in every country where those trees are cultivated The wild fig differs from the domesticated in its habits, its season of fructification, and its insect population, but is, I believe, not specifically distinguishable from the garden fig, though I do not know that it is reclaimable by cultivation. The wild olive, which is so abundant in the Tuscan Maremma, produces good fruit without further care, when thinned out and freed from the shade of other trees, and is particularly suited for grafting. See Salvagnoli, Memorie sulle Maremme, pp. 63-73. The olive is indigenous in Syria and in the Punjaub, and forms vast forests in the Himalayas at from 1,400 to 2,100 feet above the level of the sea.--Cleghorn, Memoir on the Timber procured from the Indus, etc., pp. 8-15. Fraas, Klima und Pfanzenwelt in der Zeit, pp. 35-38, gives, upon the authority of Link and other botanical writers, a lift of the native habitats of most cereals and of many fruits, or at least of localities where those plants are said to be now found wild; but the data do not appear to rest, in general, upon very trustworthy evidence. Theoretically, there can be little doubt that all our cultivated plants are modified forms of spontaneous vegetation, though the connection is not historically shown, nor are we able to say that the originals of some domesticated vegetables may not be now extinct and unrepresented in the existing wild flora. See, on this subject, Humboldt, Ansichten der Natur, i., pp. 208, 209.