44 Cwi versify of Calif ornia Pahlications. ibotaky 



streams have combined their forces in an attempt to reduce this 

 line it is still 500 to 1000 feet higher than it is on the south and 

 west sides. 



From this we are led to conclude that the prime factor affect- 

 ing the distribution of plants on San Jacinto Mountain is 

 altitude (including with this other conditions produced l)y the 

 altitude), and that second in importance, i)articularl.y on the 

 north and east sides, is the influence of desert winds, while the 

 third factor is slope exposure. We also see that these, together 

 with other factors of less importance, unite in many sets of 

 combinations on different parts of the mountain, thus producing 

 in the floral belts a great diversity of outline and position. 



A COMPARISON OF MONTANE AND DESERT CONDITIONS. 



At first thought one might suppose that the conditions 

 existing on high mountains and those prevailing in the desert 

 regions were directly opposite in their nature, but when con- 

 sidered in the light of their effect upon the plants of the two 

 regions it is seen that they are in many respects very similar. 



An example of this similarity of characters in plants from the 

 montane and desert regions, as contrasted with those of plants 

 from the intervening slopes, is seen in the three varieties of 

 Monardella macranfha collected in the San Jacinto Mountains 

 and along the desert which skirts their eastern base. 



In plate xii is shown a variety (the second one technically 

 described under Moiiardella maeranfJia in the list closing this 

 report) from the Upper Transition Zone. It grows in open pine 

 and fir forests at about 8000 feet altitude, and maybe considered 

 as the high-montane form. Comparing this with the specimen 

 shown in i)late xi it is seen to be much reduced in size owing to 

 the shortened intern odes; the leaf surface is greatl,y reduced, the 

 pubescence close and dense, ami the whole appearance is that 

 of a xerophytic plant. 



The specimen shown in i)late xi [M. macranfha fenuif^ora) is 

 from a shaded hillside just below the Lower Transition Zone and 

 therefore in the upi^er part of the chaparral l)elt. This variety 

 grows beneath larger plants by which it is partially shaded. 

 The internodes are seen to lie elongated, tlie leaves are much hirger 



