2g BOTANY. 



shall reach. Hence it does not surprise one to find the lowest limit of 

 .Coniferous vegetation ranging somewhat in this manner as one goes south : 



Feet. 



South Park, Colorado 9 > 000 



Saguache, Colorado (Pinon) 7 > 500 



Santa F6, New Mexico (Pinou) 7 > 100 



Fort Wingate, New Mexico (Pirion) 7 < 000 



Mogollon Mesa, Arizona (Pinus ponderosa) 6,500 



Mogollou Mesa, Arizona (Oak) 0,200 



Camp Grant, Arizona (Oak) 5 > 000 



Camp Grant, Arizona (Pinus ponderosa) 6,500 



Camp Crittenden, Southern Arizona (Oak) 4,749 



Camp Crittenden, Southern Arizona (Pinus ponderosa) 5,500 



In other words, where the plain breaks up into a well-defined mountain 

 range or peak which is well watered, the timber begins just above the limit 

 of the plain. 



The upper limit of forest growth, or, as it is called, "timber-line," is 

 less clearly defined. Dr. Engelmann has clearly pointed out, in "The Trans- 

 actions of the Saint Louis Academy of Science" for 1862, p. 129, that near 

 Denver it begins just at about the altitude it disappears in Alpine Europe; 

 in other words, that it ascends in our Rocky Mountain Range about as high 

 above the great plain out of which these mountains rise as it does on the 

 Alps above the ocean level : and the conclusion appears clear that this plain 

 receives the heat freely during the day, and its dry air allowing as ready a 

 radiation of it at night, it (the plain) becomes the furnace whose heat is to 

 carry the timber to so unusual an altitude. 



Dr. Engelmann further notes that the popular opinion that this upper 

 limit is carried to greater altitudes as we go south is not correct The 

 following table may throw some further light upon his statements. 

 The upper limit of trees averages between — 



Latitude 40-41° north, 7 peaks 11, 132+ 



Latitude 39-40° north, 15 peaks 11, 636 



Latitude 38-39° north, 6 peaks 11,729 



Latitude 37-38° north, 2 peaks 10, 625 



San Francisco Mountains, 35-36°, latitude north 11, 547 



*Sierra Blanca, Arizona, 33-34°, latitude north .. ..... 11,100!! 



* A portion of the material for this table I have obtained from Mr. Gannett's admirable " List of 

 Elevations'' — a paper of great labor and great value. 



