181 . 
ON THE DISTRIBUTION OF SOME WESTERN 
PLANTS.—I 
By Epwarp L. GREENE. 
I desire to put upon record here, in the first place, some 
observations upon the topographical distribution of certain 
plants common in middle California, and universally regarded 
as native there, but which demean themselves always as for- 
' eigners. A student once asked me if I considered Lepidiwm 
s _ indigenous to the region of San Francisco Bay. 
e had observed that it occurs nowhere but along hard and 
sterile waysides, in yellow gravelly soil that has been beaten 
smooth by the footsteps of men and animals; and such places 
are usually occupied by the hardiest and most irrepressible 
of alien weeds. In any country the native plants thereof are 
sought in the open field, by lake or river, or in the forest. 
That a species grows only in cultivated lands, or along the 
public highways, or about buildings, argues for it a foreign 
derivation. It seems a natural and reasonable inference that 
plants which in any district decline to plant themselves in 
virgin soil, but stay only where the plow has done its work, 
or where man has built his highways, or the domestic animals 
have beaten their paths—where the conditions of growth are 
more or less artificial—are immigrants. There are possibly 
some exceptions to the rule, nevertheless; for if the Lepidiwm 
in question be not native in the middle seaboard counties of 
California, probably no one can can say where it is indige- 
nous. And yet the observer of its behavior, if he go back, 
in imagination, to the time when this part of California had 
no old roads, or hard-beaten gravelly by-paths, will not be 
able to conceive of this plant as a denizen of this country at 
such atime. According to all that is known of its habits, a 
region not tenanted by civilized man would not have a single 
Spot of earth adapted to its growth. 
The native sorts of pepper-grass are rather numerous in 
California, but no other species, not even L. lasiocarpum, its 
Eryruea, Vol. I, No. 9 [1 September, 1893]. 
