hrat of the short summer to dissipate it. In addition the effect 

 of topography which is so great southward is largely nullified 

 bv the cold covering with a perpetual mantle of snow most of 

 the mountains where a diversified flora would alone be possi- 

 ble. 



Since cold is the chief factor in this latitudinal distribution 

 v'C expect to and do find the same changes as we ascend from 

 the sea to the mountain peaks. This change has been noted 

 from time immemorial by all acute observers. Humboldt long 

 ago laid down the general facts in his life zones which he calls 

 Tierra Fria. Tierra Caliente, etc.. by which for generations we 

 have had the life of the world divided info Torrid, Temper- 

 ate and Frigid Zones. There is little to add to this except in 

 details due to topography and the subordination of the Frigid 

 as a subdivision of'the Temperate Zone. Of this phase of the 

 case my address of a year ago dealt, and need not be men- 

 tioned here except to furnish you the results in my schedule of 

 zonal distribution appended. 



The soil of a region has an astonishingly small influence 

 on the vegetation chemically, for plants take up but a very 

 minute quantity of solid matter and can generally find what 

 ihey need in any soil, but the abundance of the needed matter 

 affects the luxitriance of grow^th. Whatever effect the soil 

 may have on the vegetation, it is independent of life zones, 

 since any kind of soil may be found in any zone. The abund- 

 pnce or scarcity of carbonaceous matter in the soil (which 

 is simply the legacy of former growths) has a marked effect 

 on the size and quantity of plants, and the presence of even 

 small percentages of soluble alkalies seriously aflFects the kind 

 of vegetation, as is shown in the flora of the alkaline deserts, 

 but on the whole the influence of the chemical quality of soil is 

 least of all the factors. The chief influence of soil in its me- 

 chanical structure. A clay soil is poor chiefly because it is 

 dense and difficult for rocfts to penetrate it, and because it is 

 almost always found on fiats which have no proper drainage. 

 The same physical elements in the shape of sand and gravel 

 iotm the chief arable land of Utah, because of their porosity. 



The wind movement has but a slight effect on the charnc- 

 'f-r of the vegetation but it has a marked effect on the dis- 

 tribution of species. The chief effect of the wind is the wide 

 distribution of species by the transportation oF seeds. This 



