176 Rhodora [SEPTEMBER — 
for the writer by Mr. H. N. Eaton, the amphibolite of the northern 
slope shows, besides hornblende and talc (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 principai 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 
discussed they must await more detailed field-study and the com- 
pletion of many chemical analyses. ’ 
e 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. 
7 Mr, Eaton’s analysis of this hook from the north crest of ge Albert is as follows: 
“A heavy, 
In thin section — ah 
5 
locrystalli “I posed of hornblende, plagioclase, and re 
The hornblende constitutes the great bulk of the rock. It is very pleochoric — och! 
yellow, grass green, and greenish blue. Some crystals are idiomorphic, while “ 
are eaten into and show inte wths with feldspar and calcite. - oclase 
Feldspar is relatively abundant in allotriomorphic prisms. It is wholly plagiocl ee 
according to both the carlsbad and albite laws is common. The albite st ere 
tions make angles of 9, 19, and 36 degrees respectively on three crystals wie 
test ; h . 7 } Hie ent 1 nd am 7 
ed; proving t p 1g 
through andesine, to basic labradorite. 
T.1 L q 1 : : + 
YY AE TeRUL 
‘ine q ¥ 31 4.4 
a tals. and seems 
rock is an amphibolite, ” 2 
? Dana, Man, Geol. ed. 4, 67 (1894), 
