New-York tribune., 1874-08-27
APPLIED SCIENCE.

PREPARATION OF ALUMINIUM.-Garnerl OF London
prepares this metal by placing a mixture of 100
marta of alumina obtained in the usual way from
kaon &c. with 40 parts of charcoal, heated to red
ness. in retorts at a dark red heat, and leading
chlorine into them from an iron gasometer lined
with lead, and closed with gas tar covered with
hydrochloric acid The volatilized chloride OF
aluminium formed is condensed in vessels OF sheet
iron glazed internally, and IS decOmposed by an
electrical current produced by maRneto-electrlc
machine The liberated chlorine is returned to the
gasOmeter.
PHYSIOLOGICAL. CLASSIFICATION OF PLANTs.-A
classification of plants, based upon physiological
characters and their relations to climatic conditions
has been recently proposed by NJ. A. De Candolle
and discussed with special reference to its bearing
upon the study of the vegetation of the globe in
mast ages He divides plants into six groups, sui-
GENTLY well characterized within general limits of
which the first includes plants requiring large
amount of heat and moisture such as are now found
in the hot damp valleys of the tropics, where the
mean Temperature exceeds S6o Fahrenheit, and
moisture is never wanting These lie designated as
Meeatherms- mainly woody plants and evergreen
climbers including forest trees OF numerous species
growing together and air-plants in comparative
abundance Fossil remains show that at very
earlv period fora of nearly identical character was
distributed over large part of the globe, but since
the beginning of the tertiary era it has become Inn
tied more and more closely to the equatorial regions
The second group (Xerophilesl requires as much
heat but less moisture, occupying the dry regions
from Southern California east and southward, GER
tain portions of South America, and in the Old World
from the Senegal to Arabia and the Indus, Australia
South Africa &c. 1t includes few trees but many
shrubberv or herbaceous perennials, and numerous
succuent plants. The third group of Mesotherms
requires more moderate degree of heat Ia mean OF
So $50 Fahrenheit and of moisture. and comprises
much of the flora of the Southern States, California
China and Japan New-Zealand and Tasmania, the
Mediterranean region, and the like, including a
great variety of orders. similar flora existed dur
ing the early tertiary period in Spitzbergen and
much of North America, the vegetation OF the United
States and Japan being then nearly identical. The
fourth group (MicrOtherms) is limited by mean
temperature of 32o-5Sc Fahrenheit, and is charac-
terzed by the abundance of deciduOus trees confers
(the forests often formed by trees OF but single
srecies), herbaceous perennas, and by the absence
of members of the preceding groups Then next group
Hckistotherms) comprises arctic or alpine plants
recurring very little heat, and able to endure the
long darkness of Winter. The orders represented
are not numerous, and woody species are compare
lively rare. A sixth group, styled Megistotherms
NAV be formed of such plants demand an extreme
degree of heat, now scarcely represented upon the
earth, but formerly including the alg@ ferns and
lycopods of the carbonferous period The cOnstitu-
tonal pecuarties of plants upon whicht grouping
is based accounted for by no COMMUNICATIONS
of either external internal structure or compost
ton. De Candoe attempts to explain them upon
the principle of heredty, the present constitution
being the result of long continued habit. He con-
sders it established fact that in the earliest ages
there prevailed over the entire globe uniform
climate of high temperature, followed by very
gradual cooling and the establishment by slow de-
gress of distinct and localized climates. He as
sunes as a necessary consequence that the earliest
flora must have been general and as uniform, con-
sisting wholly of MegistotheTms. which, as the
Temperature declined were gradually driven from
the poles toward the equator, their place becoming
occupied by the other groups successiyely or as cir
cumstances favored. In what way the several
groups were developed is question kindred to that
respecting the evolution of specific FORMS and the
hypothesis of Darwin is equally applicable in its
solution. The correctness Of that hypothesis DE
Candolle does not consider, but he expresses the
opinion that it is the only hypothesis worthy of dis
cussion that has vet been advanced.