VOL. I. | Naturalized Plants. 31 
twenty of them, have either come to us, or have passed ost the 
condition of mere adventive plants to that of naturalized ones, in 
the period of twelve or fifteen years that have elapsed since the 
material was accumulated on which that great work was founded. 
That nearly one-quarter of the naturalized flora of the region 
should have been added in this short time is a notable fact, but 
quite in harmony with the great increase of population and the 
wonderful industrial development during the same period. 
Sixty-two species of the entire seventy-eight, including all the 
Cruciferze and all but one of the grasses, are of European origin, 
and the same proportion holds if the commoner plants only are 
considered. Fourteen are natives of other parts of America, twelve 
of them coming from the South and two from the North, a pre- 
ponderance agreeing with the derivation of the native flora. Asia 
and Africa supply two species each, and Australia one. 
This statement, however, does not correctly represent the imme- 
diate sources from which most of these plants have been received. 
Many of them have long been dispersed from their primitive homes, 
and are weeds of world-wide diffusion. These are for the most 
part attributed to Europe, although the real nativity of some of 
them is very uncertain, and they have doubtless reached us through 
_ intermediate countries. It is probable that the only direct importa- 
tions are those few plants which are not likewise naturalized either 
in Mexico or in the transmontane States of the Union, the former 
being the intermediary through which the earlier introduced and 
more abundant species have been received, while more recent emi- 
grants have come by way of the latter. 
The four counties here, called Southern California, constitute one- 
fifth of the entire area of the State; a territory a little larger than 
Ohio. But of this great province only one-tenth is arable land, a 
district hardly more than half the size of New Jersey.* 
*AREA OF SOUTHERN CALIFORNIA. 
Arable. Mt. and Desert. Total 
é sq. m. sq. m. sq. m. 
DAD TORO. Olas oa ee Wei cece ees 836 14,133 14,969 
Orange 5.0: . <5 BON OU US Oyateas Ce 450 304 754 
en PIER os i sh vse se pee eek 1,000 2,996 3,996 
. San Bernardino..........++.see0see ees 2,000 19,170  . 21,170 
4,286 36,603 40, 889 
“The arable parts of Los Angeles and San Bernardino are estimated. 
