FORESTS OF SAX JUAN ISLAND 170 



the soil on those portions of Cattle Point Hill and South Hill 

 where the forest has failed to grow "is gravelly and bears the 

 flora of the outward prairies" and has suggested that although the 

 wind is of some importance in the ecological problem in\'olved 

 "the difference in soil on the two slopes is the chief cause for the 

 difference in forest distribution." 



This suggestion led the writer of this paper to investigate, dur- 

 ing the summer of 1911, the character of the soil on the barren and 

 the forested portion of these four elevations. He had made obser- 



Fig. 2 Cattle Point Hill from the west, showing the forested north slope 

 and the treeless south slope. The low treeless ridge is in the foreground (pho- 

 tograph by Dr. T. C. Frye). 



vations on the evident effect of wind on the trees on Cattle Point 

 Hill in 1908 and 1909. It was found that in all four of the cases 

 the soil on the barren portion of the elevation is black and pow- 

 der}', containing a good deal of gravel, while the forested portion 

 is everywhere covered with 2 feet or more of yellow cla}' contain- 

 ing occasional irregular fragments of rock. This layer of claj' is 

 largely free from gravel. At its surface is a few inches of forest 

 humus. Beneath this clay, the character of the soil is much the 

 same as it is at the surface on the barren portion of the elevation. 

 In all four of the cases discussed in this paper, it was found that 



