VOL. III.] Forms of Trees. 5 



Pinaster), Lebanon cedar, and the hundreds, if not thousands, of 

 other evergreen trees which inhabit regions below the regular snow 

 line. 



Nature thus eliminates from snow-visited forests all evergreen 

 trees which are not suited to resist the pressure of the snow. On 

 the contrary, the snowfall makes it possible for all those trees to 

 live and survive which, through their outward form, are able to easily- 

 shed the accumulated snow. As regards deciduous trees, no such 

 upright trunks and sloping branches are necessary, as the bare limbs 

 do not accumulate the snow, nor suffer under pressure. If the 

 above is true, the forests of snow-visited districts will be found to 

 consist of only such varieties of trees as possess the requisite form, 

 that is, evergreen trees with upright, undivided trunks and down- 

 ward sloping branches, as well as of deciduous trees of various not 

 especially characteristic forms. Upon examination this will also be 

 found to be the case. 



A visit to the high pine forests of Sierra Nevada shows us just 

 such forests. Nowhere is the snowfall heavier and nowhere is the 

 characteristic form of the evergreen trees more pronounced. This 

 is also the case in all other show- visited regions where forests are at 

 all able to exist. Where the snowfall is the heaviest and lasts the 

 longest, all evergreen trees, at least during a certain period of their 

 life, possess the required pyramidal form. Evergreen trees of any 

 other form would in their struggle for existeace have little or no 

 chance to compete with better equipped neighbors. It follows, 

 also, that the less the snowfall the less characteristic will prove the 

 pyramidal form in all evergreen species, while lower down the 

 mountains on the warmer slopes the pyramidal form may be ex- 

 pected to be entirely absent. 



To refer to our nearest high mountains, the Sierra Nevada, we 

 find thus on the snow-belt such trees as Abies Douglasii, Picea ama- 

 bilis, Pimis Lambertiana, Libocedrus decurrens. Sequoia gigantea, 

 etc. All these show in a characteristic way the pyramidal form, the 

 snow-shedding branches and the undivided trunk. We find in this 

 region no large live oaks, nor any large evergreen trees of globular 

 or goblet shape. But in the region immediately below the, heavy 

 snow belt, the characteristic pyramidal shape is entirely absent. 

 The forms of the evergreen trees are here evidently regulated by 

 other agencies. In this region we meet with several evergreen 



