* 
1885.] ; Botany. 397 
and distribution, as the climate and topography of Eastern Amer- 
ica differ from the climate and topography of the Pacific slope. 
The causes which have produced the dissimilar composition of 
these two forests must be sought in the climatic conditions of a 
geological era earlier than our own and in the actual topographi- 
cal formation of the continent. 
The forests of the Atlantic and the Pacific regions, dissimilar 
in composition in the central part of the continent, are united at 
the north by a broad belt-of sub-arctic forests, extending across 
the continent north of the fiftieth degree of latitude. One half 
of the species of which this northern portion is composed, ex- 
tends from the Atlantic to the Pacific; and its general features, 
although differing east and west of the continental divide, in con- 
formity with the climatic conditions peculiar to the Atlantic and 
the Pacific sides of the continent, still possess considerable uni- 
formity. The forests of the Atlantic and the Pacific regions are 
also united at the south by a narrow strip of the flora peculiar to 
the plateau of Northern Mexico, here extending northward into 
the United States. Certain characteristic species of this flora 
extend from the Gulf of Mexico to the shores of the Pacific, and 
the outposts between the Atlantic and the Pacific regions.—Fro- 
fessor Sargent in Vol. ix of the roth Census of the United States. 
FERTILIZATION OF THE LEATHER-FLOWER (CLEMATIS 
THE 
VIORNA).—The leather-flower is a rather™curious plant, climbing 
by means of its leaf-stalks among the low underbrush. The 
-flower (Fig. 1) it bears is bell-shaped and hangs pendent from a 
somewhat long peduncle, which extends in a horizontal direction. ` 
It has no petals ; four sepals taking their place. These are very 
thick and leathery, and are colored purplish without. The edges 
and inner part of the sepals are white. The tips are recurved, 
and these, together with the white edges of the sepals, perhaps 
serve as guide marks, directing the insect to the entrance below 
as a means of obtaining the honey. The bee, which I find to be 
the fertilizing agent, holds to the recurved tips of the sepals 
while effecting its honey-gathering, and this is the more obvious 
purpose of these tips. The outer stamens begin to open 
then those next within, being in advance of the pistils. 
But before the inner stamens are ready to shed their pollen, the 
stigmas are also ready, so that were it not for a very ingenious 
