146 The American Naturalist. [Febrony, 
late paper this writer communicates the results of the examination of 
crystals of hematite produced by sublimation in smelting furnaces and 
those from San Sebastiano, Italy, that are supposed to have been formed 
in an analogous manner. In all of these the habit is the same, 
although different combinations of nearly related forms occur on them. 
Sublimed valentinite and senarmontite are likewise studied. Cuprite 
produced by slow oxidation at a low temperature has an octahedral or 
dodecahedral habit, while that produced at a high temperature is 
probably hexahedral. Struvite obtained from a solution of Koch's 
peptone differs materially from the natural mineral, but the differences 
have not yet been carefully enough studied to warrant any general 
conclusion being drawn from the observations. Further articles from 
Prof. Arzruni will be looked for with interest. 
BOTANY. 
The Relative Altitudes of the Rocky and Appalachian 
Mountain Systems as Influencing the Distribution of 
orthern Plants.—In the study of the geographical distribution of : 
North American plants certain difficulties have been apparent smo — 
the adoption of three ‘‘regions,’’ extending north and south, ny 
denominated respectively the eastern, central, and western. A per 
ee 
ba . » . . i 1 
better division of the continent is that proposed by Britton, 
recognizes a northern region, including British America, the Sier: 
the Rockies, and the Alleghenies; and a southern region, DE 
the Atlantic coast, Mississippi valley, and a part of California. N 
only does such an arrangement of regions make it possible to gro 
more correctly the known facts of spermaphytic distribution, but, 1o i 
certain extent, it corresponds more exactly with the probable me" 
of original distribution of all plants over the continental area oF pean j 
America. Since the glacial period the great drift-covered gery 
been covered with vegetation, spreading slowly from Siberia and Uae 
dinavia on the north, and from Mexico and South Amei 
south. The flora of North America, then, exclusive of ef oe 
the south, 
T 
rE en 
the most part, a resultant of the greater or less comminglin 
two currents of vegetation, the one flowing constantly to ne Si 
other as constantly flowing northward. east 
_ 1 The General Distribution of North American Plants; by N. S. Britton- — 
of the American Association for the Advancement of Science. 1890. 
