April, 1919] 



Beginnings of Revegetation 



323 



I 



of numerous gullies washed in the ash areas where it was so 

 deep that nothing could come through on the level. Observation 

 of such places shows that it can penetrate deposits up to about 

 three feet in thickness. The horsetail is not, however, of 



anything like the 



importance in Kat- 

 mai Valley that 

 it is at Kodiak.* 

 The deposits are 

 for the most part 

 so thick that it is 

 only here and there 

 that even the horse 

 tail could grow 

 through them. 

 (See picture.). 



Second, the 

 patches of surviv- 

 ing herbage serve 

 as a wind break 

 in the shelter of 

 which new seed- 

 lings can start. 

 This again is a 

 function of consid- 

 erable importance 

 locally as will be 

 seen from the dis- 

 cussion to follow. 

 Third, the oases 

 of resurrected veg- 

 etation furnish the 

 seed which may be the basis for starting new vegetation in the 

 desert round about. This, however, is not a factor of great 

 consequence in this case. The plants have come back on the 

 steep mountains, from which the ash quickly slid off, so much 

 more freely than in the deeply buried valley that they would 

 furnish abundant seed, even if nothing had survived on the 

 flats. Most of the plants of the district have seed adapted 



Photograph by Robert F. Griggs 



EQUISETUM COMING THROUGH IN THE BOTTOM OF A 



GULLEY WHERE THE DEPOSIT WAS TOO THICK 



FOR IT TO PENETRATE ELSEWHERE. 



*See the first paper of this series, p. 43. 



