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JOURNAL OF FORESTRY 



May and June, which has an average value of 2.6 per cent at a depth of 

 15 cm. on south-facing slopes at 7,000 feet. The writer has frequently 

 seen large numbers of dead seedling pines at about this elevation during 

 the latter part of June, when the culminating effects of the arid fore- 

 summer were being exerted. There is much observational evidence to 

 support the indication of these figures that the conditions for seeding 

 and germination of yellow pine are better at about 7,000 feet than they 

 are at higher or lower elevations. The relatively large number (2,525) 



Fig. 3. — Graphs showing the total number of adult trees on six areas of the slope exposure 

 and altitude indicated. Hatched portions indicate species other than Arizona yellow pine. 



of seedlings at 9,000 feet comprised 2,079 yellow pines, but a large pro- 

 portion of them had reached their second and third year of growth. 



The data exhibited in figure 2 show that the number of trees which 

 are well established, but still small, is about the same at all the lower 

 elevations, but is pronouncedly greater at 9,000 feet. Observation 

 throughout the forested portion of the mountain confirms these figures 

 in their indication that the number of small and well-established pines 

 is greater on the highest slopes of Mt. Lemmon than it is in the rela- 

 tively open and park-like bodies of timber at lower elevations. 



