April, 1919] 



Beginnings of Revegetation 



333 



mulch, prevents evaporation. It has not proved practicable 

 as yet to submit this hypothesis to experimental test, but it 

 has been found that it is impossible to obtain in pot cultures 

 from small quantities of ash anything like such vigorous growth 

 as occurs even in dry places in the field where the plants have 

 unlimited possibilities of root extension with the consequent 

 ability to draw upon wide areas for the necessary quantity of 

 salts. 



Photograph by Robert F. Griggs 



SEEDS COMING UP WHERE COVERED UP BY THE OUTWASH 



OF A TEMPORARY STREAM. 



General surface of the ash bare. Lower Katmai Valley. 



SEEDLINGS IN DRY WATER-LAID DEPOSITS. 



The distribution of only a portion of the new plants can, 

 however, be accounted for on this hypothesis. Those coming 

 up in outwash deposits are often so situated as to be kept 

 better drained than the surrounding level. (See cut above.) 

 At first I was inclined to suppose that such deposits were suffi- 

 ciently contaminated by admixture of the original humus soil 

 washed off the mountains along with the ash to present quite 

 different and altogether more favorable conditions for the 



