ee 
1904] SPALDING—THE CREOSOTE BUSH 133 
roots. Compare the diagram, fig. 7, showing the position and dis- 
tance of a Parkinsonia, Fouquieria, Opuntia, and another Covillea. 
The roots were traced more than half the distance to the Parkinsonia 
in one direction, and to the Fouquieria in the other. 
* 4 
vot hy, 
Lag 
Fis. 6.—Covillea from plain to the north of the Desert Laboratory, showing char- 
acter of root system. 
From these and many other individual plants that have been 
examined, it has been found that the general plan of the root system is 
essentially the same in all; there is a strong tap-root which grows 
downwards until it meets an obstruction, or for some other reason 
changes its course, and slender lateral roots which run near the sur- 
