28 PETRIFIED FORESTS. 



produced beaut. ful sections when cut and polished. One such petrified 

 forest is in the Sahara in Africa and the other in the Territory of Ari- 

 zona. In these cases forests had existed where there is now only desert. 

 A modern instance of somewhat similar purport is 

 the burnt and dead forest on a southeast spur of San Bernardino. 

 This forest was killed by fire nearly fifty years ago. It is now without 

 renewal. Valuable forms of our forest vegetation in Southern Cali- 

 fornia probably had their origin somewhere else and have been intro- 

 duced here from the north. It is reasonable to assume that all forest 

 forms were evolved on comparatively level plains and that mountain 

 forms have been modified by slow elevation and change of climate and 

 condition. In most parts of Southern California we are too near the 

 edge of conditions favorable to forest growth to take any chances on 

 allowing important forests to be destroyed. All our forests are on 

 steep watersheds, all are of the highest importance and therefore with 

 us the demand is for the preservation of all our forests. 



