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IOWA ACADEMY OP SCIENCE 
as we advanced. At the forest line most of the above- named 
species are still abundant, together with several others that be- 
long more properly to the Arctic zone. 
It should be noted that at this elevation, about 2500 meters, 
where Tstiga mertensiana and Finns albicauUs dwindle down 
into low gnarled shrubs, there may be found open southward 
slopes, where certain Canadian plants, or even of lower zones, 
can maintain an existence, such as Finns contorta, Bihes cereum, 
and Spiraea densiflora. This, of course, is saying merely that 
the life zones are not necessarily altitudinal zones, but are of a 
somewhat isothermal character. 
The species most characteristic of the Arctic zone, that is, 
those occurring more or less plentifully at 2700 meters and up- 
ward and not found abundantly below timber line are, Anemone 
huds'oniana, Oxyria digyna, Braha aureola, Fhyllodoce glanduli- 
fera, Collomia debilis, Sibbaldia cnneifolia, Erigeron compo- 
situs, and ail undetermined Senecio. In addition to these, a 
number of species plentiful in the upper Hudsonian were also 
found, — Carex straminiformis, G. breiveri, Folygonnnv new- 
berryi, Erigonum pyrolaefolium, Spraguea umbellata, Saxi- 
fraga tolmiei, Fhyllodoce empetriformis, Fentstemon menziesii 
davidsortii, and Anlennaria media. It was: too early in the sea- 
son to study the Arctic flora to good advantage, as comparatively 
very little of the ground lying well within this zone was. un- 
covered by snow. The mountain, moreover, is relatively young, 
and the soil above timber line is so scanty that it cannot sup- 
port a very copious vegetation. 
From this very brief account some idea may be gained of 
the altitudinal limits of the several life zones represented in 
this section of the Cascades, and of a few of the most character- 
istic species of each. From this region of, copious moisture we 
will now pass on to a somewhat more detailed consideration of 
the plants of the eastern slope, where, within a few miles, we 
encounter an enormous decrease in the precipitation. 
We started eastward again on July 19, and soon came to the 
edge of a vast lava fleld, which, spread out before us in black 
and rugged desolation, presented a truly remarkable geological 
spectacle. Two or three of the craters from which the most 
recent flows had issued could be made out easily. The dark 
jagged blocks of lava were tilted and tumbled in the wildest 
confusion, apparently just as they were left when first split 
and upheaved by the movement of the deeper and more fluid 
