April, 1919] 



Beginnings of Revegetation 



327 



These lupines are, however, strictly confined to the valley 

 and to situations that at one time or another have been over- 

 flowed by stream waters. On the surrounding hillsides and in 

 other parts of the valley there are many areas that, to all 

 appearance, offer quite as favorable habitats as those which 

 are occupied by lupines, but not a single plant has ever been 

 detected outside the flood plains except on oases of old soil. 



The reason for this peculiarity of distribution is' not clear at 

 the present time. It may be that the seeds are water borne 



Photograph by D. B. Church 



SEEDLINGS OF EPILOBIUM ALASKA STARTING ON PUMICE 



IN A SPRINGY PLACE. 



instead of wind disseminated. But the winds of the district 

 are so extremely violent, (see below, page 339), as to make it 

 appear unlikely that objects so slight as lupine seeds would 

 resist their action. Legumes in general are known to be 

 dependent on organisms in the soil for that innoculation with 

 the tubercle bacteria upon which their success is dependent. 

 It might well be that while these organisms were absent from 

 the general mass of ash they were present in ash contaminated 

 by flood waters. 



