06 
zones, the Juniper, Deciduous Oak, Spruce and Frigid. In my » 
Geography of Utah, published in 1902, I published ne ee 
cae corresponding to our Spruce, and Frigid, which in- 
cludes not only the Arctic plants but the Alpine plants as well. 
The upper temperature limits of the Lower Temperate life zone 
are approximately 52% annual mean. The upper .\.iddle Tem- 
perate limit is approximately 46° annual temperature. The Up- 
per Temperate life zone limit is not much above 32° and the grow- 
ing period is therefore very short, belonging to the zone above 
it, the Erigid, 
s practically impossille for the novice and decidedly diffi- 
cult for the skilled botanist to determine the limits of the life zones 
experimentally in the field without having some characteristic 
plant as his guide. This is why both Merriam and myself have 
used certain plants which are characteristic of certain iife zones, 
as zonal plants, though neither of us originated the idea. Merriam 
zonal plant for the reason that it is relatively scarce compared with 
the juniper. I therefore use the juniner as my zonal plant. Mer- 
riam has used the Larrea as the zonal plant for his Lower Son- 
ofan, which as I have said is the true Tropical life zone in our 
region... No better selection than this could be made. In the selec- 
tion of a zonal plant for the Middle Temperate (Transition of 
Merriam) the deciduous oak is the most conspicuous, but unfortu- 
ee disappears both west and north of the Oquiirh mountains. 
€ spruce and firs are good zonal plants of the Upper Temper- 
ate. The: Frigid or Alpine life zone includes the subalpine and 
treeless regions and meadows z the high peaks and Arctic and 
needs no charcteristic.zonal plan 
Beginning then with our see plants, we find the Larrea or 
creosote bush abounds throughout our Trop al region and comes 
to a sudden stop in a region where the annual temperat re is less 
than 60° Fahrenheit. There will be, of course, mountain ranges 
whose southern and hot slopes will have the Larrea growing high 
ap. on that slope and low down on the northern slope. There will 
o-be places where streams flow down through canons far into 
the: Tropical life zone where temperate plants only grow. A mo- 
