Jan., 1919] Effects of the Eruption on Vegetation 



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ground, forming a rosette or mat. (See below.) An inves- 

 tigation of the physiological causes by which this reaction is 

 brought about would yield exceedingly interesting results if one 

 could find the means of attacking the problem. A satisfactory 

 solution should throw much light on the causes underlying the 

 development of prostrate shrubs in general, such as the pros- 

 trate juniper of the north and the prostrate yew of our own 

 woods, both forms being closely related to erect growing species. 





I'hotograph by R. F. Griggs 



Before the eruption Salix nuUallii grew as an upright tree. The tops were killed 

 and the new growth forms prostrate mats on the surface of the ground. 



