Vol. i No. 12 



TORREYA 



December, 1901 



ON THE RELATION OF REDWOODS AND FOG TO 



THE GENERAL PRECIPITATION IN THE 



REDWOOD BELT OF CALIFORNIA 



By W. A. Cannon 



It is well known to all dwellers in regions which are frequently 

 covered by fog that fog acts to conserve, as well as to increase, 

 the general amount of moisture, and while, so far as I know, no 

 data have been compiled touching either of these effects, they 

 undoubtedly play an important part in the plant life of the region. 

 This is well illustrated by the inland distribution of the redwood 

 on the west coast of the United States. As is well known, the 

 redwoods occur in the fog-belt of the northern half of California, 

 and are confined in a markedly restricted manner to those por- 

 tions of the coast mountain ranges, such as ravines, which, on 

 account of favoring topographical conditions, the fog may reach. 

 The restriction of the distribution to so narrow a zone is, per- 

 haps, not due so much to the negative factor, the conservation 

 of moisture already present, as to the positive one, the actual 

 precipitation of water from the fog. While this, without ques- 

 tion, is an important factor in the total precipitation in any 

 region subject to fog, it becomes very much more marked, I am 

 convinced, in that region where the redwood forests are found. 

 The reason for this lies in the character of the foliage of the red- 

 wood. Because trie leaves of the redwood are small and closely 

 set together on the twigs, and because both twigs and leaves are 

 relatively delicate, the boughs which they help to form are fern-like 

 in general appearance and constitute a very effective filter, by which 



[The exact date of publication of each issue of Torreya is given in the succeed- 

 ing number. Vol. I, No. n, comprising pages 125-136, was issued November 25, 

 1901.] 



