voL.i] Hall. — Botanical Survey of San Jacinto Mountain. 11 



zones and when it is known to what zone any locality belongs 

 the crops which wonld probably best thrive there may be pre- 

 dicited, and much time and money, which would otherwise be 

 spent in experimenting, may thus be saved. 



But in the study of plant geography the botanist finds that 

 he can make use of these life zones for another purpose. In 

 giving the range of any species of plant there is, in our opinion, 

 a decided gain in definiteness when it is placed in its proper zone, 

 and we believe that this will lie more and more appreciated as 

 botanists come to give more attention to the subject. The state- 

 ment, for example, that a particular species occurs throughout 

 the Transition Zone is much more definite than the statement 

 that it occurs between 5000 and 7000 feet altitude ; since the belt 

 between 5000 and 7000 feet on one mountain may, on account of 

 its latitude, the proximity of desert areas, etc., be a sweltering, 

 brush-covered slope, while on another it may be a cool, forested 

 area, or, if far north, even a bleak mountaiutop above timber- 

 line. In fact there is usually considerable dififereuce between the 

 climatic conditions of two places of ecjual altitude on the same 

 mountain in case they are on opposite sides. On the other hand, 

 the term ' ' Transition Zone ' ' always refers to a belt which is 

 neither extremely hot nor extremely cold, where such conditions 

 prevail, for example, as would produce forests of Yellow Pine or 

 White Fir. It is chiefly for this purpose that the life zones of 

 San Jacinto Mountain have been w^orked out and mapped (see 

 plate ii), and continual reference to these zones will be found in 

 the last cha])ter of this paper, where the ranges of the species 

 occuring on the mountain are given. 



Most botanists apjireciate the need of some such designation 

 of the floral belts which are found on all mountains, but a few 

 have objected to the use of the term " zone " in this connection 

 and would not place the plants of the higher mountains in the 

 same group with those of the Arctic regions, for the reason that 

 certain conditions, such as atmospheric pressure, are not exactly 

 the same in the two places. Although the truth of this is realized 

 still the difference is slight as compared with that between the 

 various life zones themselves and also, since latitude may be taken 

 into consideration when working in the far north or in th<» far 



