170 



near the crest of an active blowout are constantly being un- 

 dermined, and slide down with the loose sand towards the bot- 

 tom (PI. XVI.). They are not killed directly by this, but are 

 frequently seen alive near the bottom, and in this way are di- 

 rectly available in holding the sand. 



TABLE VIII. BLOW SAND. 

 (Fixation just begun.) 



Sporobolis cryptandrus 

 Chrysopsis camporum 

 Cassia chatmecrista 

 Ambrosia psilostachya 

 Monarda punctata 

 Euphorbia Geyeri 

 Cyperus Bushii 

 Paspalum setaceum 

 Commelina virginica 



d*d d c d 



d d c d d 



d c a c c 



c d c d d 



o o o a a 



d o o o o 



o o o o a 



o o a o o 



o o o o a 



TABLE IX. BLOW-SAND. 



(Nearly fixed.) 



But one other result of the movement of the sand remains 

 to be considered, and that is the effect of the blow-sand on the 



See p. 159. 



