264 Naturalized Plants. [ZOE 
added and continues, both on the mainland and on the islands, even 
below the southern boundary of the State. It is reinforced on the 
islands off San Pedro by the third species, which reaches the shores 
of the continent at San Diego. Thus at the latter place all the spe- 
cies are found, and they successively drop off as a more northerly 
latitude is attained. This isa natural arranegment for the species of 
an indigenous genus, and quite in harmony with the distribution of 
the southern flora. As the result of mere chance introduction it is 
not so easily understood. 
Their topographical position is equally indicative of an indige- 
nous origin. They are not the occupants of the waste ground of 
seaports, but mostly of a rugged coast, and of the lonely islets which 
lie in sight of it. They are as abundant in the wildest as in the 
more settled parts of the coast, and since the earliest mention of 
them notices their abundance, it is probable that they were then as 
fully established as now. They are especially plentiful on the | 
_ islands, on each of which, if exotic, a separate introduction would 
be necessary. 
The-manner whereby their wide dissemination could have oc- 
curred is likewise hard to account for. Fruit and seed are un- 
provided with means for attaching themselves to the coats of ani- 
mals, so that the convenient sheep cannot be made to bear the bur- 
den of their transportation. They are equally destitute of other 
means of locomotion. . 
__ The wide diffusion of the plants makes it necessary to place their 
introduction at the very earliest period of the Spanish settlement, 
and even then but scant time is afforded for their spread over sea 
and land to the great territory they now occupy. And how could 
the original introduction have occurred? Hardly as escapes from 
cultivation, which could only have been as ornamental plants, a 
character to which none have very strong claims and one none at 
all. Nor does the state of society at that time favor such a theory. 
Their reputed native sources, when the course of early Spanish 
commerce is considered, is averse to the supposition that they ce 
might have begun as ballast plants. What traffic there was then 
was not with Europe, but with the ports of Mexico and the other 
Spanish possessions, and it is through these countries that the Med- | 
iterranean contingent has reinforced our native flora. But there is_ - 
ho record of the presence of the ice-plants at these intermediary 
