1904} SPALDING—THE CREOSOTE BUSH 125 
has acquired habits that enable it to withstand excessive drouth, but 
has never lost its capacity to absorb and use large quantities of water, 
and attains its best development only under such conditions. 
The readiness with which this species accommodates itself to an 
over-supply of water is shown by a simple experiment. Seedlings 
of Covillea were grown in a flower pot, and after they had made a 
IG. 2.—Branches of Covillea; on the right from a well watered bush near St. 
Mary’s Sanatorium, north of the Desert Laboratory; on the left from the exceedingly 
dry soil of the mesa close by. 
good start were set into a can of water, the bottom of the pot having 
been broken through in several places. After three or four weeks 
it was found that some of the roots had grown down into the water 
and, in contrast with those growing in the soil, had taken the form of 
water roots, being entirely destitute of root-hairs. The epidermal cells 
exhibited plasmolysis with a 4 per cent. solution of potassic nitrate, 
thus indicating their capacity for active absorption. Seedlings 
grown in the Geneva tester also sent their primary roots down into 
the water without apparent injury. It is plain, then, that the roots of 
