April, 1919] Beginnings of Revegetation 325 



had started in 1915 and, having persisted even in deep pumice 

 deposits, were flowering and seeding abundantly in 1916; while 

 in 1917 considerable areas as far up stream as Martin Creek 

 were sparsely occupied by fruiting lupines, furnishing the 

 basis for an increasing rate of re vegetation. 



LUPINES THE MOST EFFECTIVE PIONEERS. 



While the new vegetation in the lower valley consists of 

 many species of plants, in the more exposed places lupines are 

 the only pioneers. (See pages 324 and 335). For this role 

 they are well adapted, because of their large heavy seeds 





Photograph by Robert F. Griggs 

 A LUPINE ON THE PUMICE FLAT AT MARTIN CREEK. 



These plants first appeared in 1915. They were well provided with root tubercles 



and grew thriftily, fruiting freely in 1917. The soil is 



almost entirely without organic nitrogen. 



which lodge where smaller seeds are blown away. On germina- 

 tion, moreover, their large supply of stored food enables them 

 to grow into strong plants much more quickly than the other 

 species present, But their capacity of utilizing atmospheric 

 nitrogen through their root tubercles is probably the decisive 

 factor, for the ash is almost devoid of nitrogenous compounds. 2 

 Lupines growing in pumice show an abundant development of 

 root tubercles which must give their possessors enormous 

 advantages over ordinary plants in the process of re vegetation. 



2 Shipley, J. W. The Nitrogen Content of Katmai Ash. Paper No. V in 

 this series, pages 213-223. 



