^-. 







A B 



A. Covillea tridentata from bajada at north base of Tumamoc Hill. Horizon- 

 tal and vertical extensions of roots of this plant shown in fig. (i. 



B. Covillea from flood-plain near West Wash, showing the large number of 

 slender adventitious roots springing from upper part of roots and long tap-root, of 

 which only a portion appears. 



C. Fouquieria splendens from bajada near where Covillea shown in A was 

 growing. Horizontal extension of roots of this plant shown in fig. S. 



