176 Rhodora [SEPTEMBER 
for the writer by Mr. H. N. Eaton, the amphibolite of the northern 
slope shows, besides hornblende and tale (a silicate of magnesium), 
calcite (carbonate of lime) and a lime-soda feldspar. In the 
soil of this slope, then, potassium and calcium are found in such 
proportion, apparently, as to account for the presence of a few species 
each of the plants (24 of the potassic rocks, 11 of the calcareous) 
which ordinarily are found only on soils high in one or the other of 
these two elements. 
But the chief interest of the north slope of Mt. Albert is in the fact 
that by far the most abundant mineral in the rocks is hornblende, 
which has as its principal constituents silica, magnesia, protoxide of 
iron, and lime.? Yet, so far as observed, none of the distinctive plants 
of the serpentine (magnesian) area of Mt. Albert extend across to the 
hornblende (also magnesian) area. This is obviously due to the 
hardness and slow decomposition of the hornblende as opposed to 
the softness and rapid decomposition of the serpentine, but detailed 
chemical analyses of the soils and plant-ashes, now under way, by Mr. 
H. H. Bartlett, will, when completed, furnish more satisfactory conclu- 
sions as to the exact conditions. Similarly, many questions somewhat 
outside the intended scope of the present preliminary paper have 
presented themselves for solution, but before they can be appropriately 
diseussed they must await more detailed field-study and the com- 
pletion of many chemical analyses. 
The foregoing discussion, however, of the relation of our alpine 
plants to the chief soil-constituents of the rocks upon which they 
grow, establishes very conclusively the fact that the alpine plants 
are much more dependent upon the chemical constituents of the soil 
than has been generally supposed. 
! Mr. Eaton's analysis of this rock from the north crest of Mt. Albert is as follows: 
“A heavy, black schistose rock containing hornblende and feldspar. 
In thin section — a holocrystalline rock, composed of hornblende, plagioclase, and talc. 
The hornblende constitutes the great bulk of the rock. It is very pleochoric — light 
yellow, grass green, and greenish blue. Some crystals are idiomorphic, while others 
are eaten into and show intergrowths with feldspar and calcite. 
Feldspar is relatively abundant in allotriomorphic prisms. It is wholly plagioclase. 
Twinning according to both the carlsbad and albite laws is common. The albite stria- 
tions make angles of 9, 19, and 36 degrees respectively on three crystals which were 
tested; proving the species to have a range between a mixture of oligoclase and andesine, 
through andesine, to basic labradorite. 
Tale occurs abundantly in irregular masses between the hornblende crystals, and seems 
to be a product of hornblende decomposition. 
The rock is an amphibolite. ” 
? Dana, Man. Geol. ed. 4, 67 (1894), 
