129 
Actinella Bigelovii, Gray, Northern Ariz. 
AcHnella biennis^ Gray, Central Ariz. 
Actbiella Rusbyi^ Gray, Northern Ariz. 
Dysodia Cooperi, Gray, Western Ariz- 
Hymenatherum polychcetum, Gray, Central N. M. 
Artemisia frariserioides.GxttxvQ, Mogollon Mts., N M, 
Artemisia Bigelovii^ Gray, Northern Ariz. 
Tetradymia glabrata^ Gray, Northern Ariz. 
Senecio Neo-Mexicaiiiis, Gray, Central N. M. 
Senecio tomentosus, Mx., Clifton, South-eastern, A. T. 
Senecio Rusbyi, Greene, Central N. M, 
Perezia Wrightii, Gray, N. M. and Central Ariz. 
Lygodesmia spinosa^ Nutt. Northern Ariz. 
Lactuca pulchclla, HBK, Northern Ariz. 
Taraxacum officinale, Weber, Prescott, Ariz. 
It may be well to make these notes the text of a few remarks on 
the topographical relations of Northern Arizona, as bearing on the 
constitution of its flora. The north-eastern portion of the Territory 
forms a continuation of the high land of Utah, the plateau terminat- 
ing suddenly in a line extending from the western termination of the 
Colorado Canon, south-eastward to the south-western portion of New 
Mexico. This line is very irregular, and exceedingly abrupt, pre- 
senting a series of broken precipices, often from i,ooo to 2,000 it^i 
m height. To the eastward th?s plateau is pretty intimately connected 
with that of New Mexico, the shallow and gradual valley of the Little 
Colorado forming an avenue for, rather than a barrier to, an inter- 
change of species. With the mountains of South-western New Mexico 
a direct connection is found in the forest-belt which skirts the edge 
of the plateau, and is known, at least in the north, as the San Fran- 
cisco Forest. We should look, then, in Northern Arizona, for the 
representatives of four quite distinct floras, and these we actually 
find, all of them being represented in the short list given above. 
The Mohave Desert is connected by a rather gradual slope with the 
north-western section, but this slope at length ends abruptly at the 
base of the north-eastern plateau as above described. On this low- 
land we find many species characteristic of the South-Californian 
deserts. In the list, Dysodia Cooper i^ not before reported from East 
Colorado River, represents this immigration. The plants of the com- 
paratively low land of Central Arizona, such as Coreopsis Driimmondii^ 
Hehanthus Maximiliani and Perezia Wrightii^ also encroach, here 
in the west, on the northern section, but are elsewhere very effectu- 
J phecked by the line of cliffs, so that on the plateau above, all the 
^ffitities are with the north, east and south-east, I point in the list 
lo Lo nicer a involucrata^ Artemisia Bigelovii^ Tetradymia glabra ta^ 
Lygodesmia spinosa and Erigeron glabellus as well marked illustra- 
tions of this southern encroachment, all being now for the first time 
j'eported from south of the Arizona line. The last named has doubt- 
less made its way into New Mexico by way of the elevated forest-belt 
deferred to. From the plains of New Mexico, Ktihnia eupatorioides 
and Bigelovia Drummondii have moved westward, the latter obvi- 
ously traveling down the Colorado Chiquito, while that Territory 
