1905] CANNON—WATER-CONDUCTING SYSTEMS 403 
irrigated plant is growing by an irrigating ditch. Its roots are 
without question in a soil which is saturated with water all of the year. 
A third specimen, not figured, was originally chosen for study as 
being representative of the irrigated form. It was placed near an 
irrigating station and was supposed, therefore, to have received 
considerable water. When I examined the conductive system of 
this plant I found it to be essentially the same as the non-irrigated 
specimen. It was learned on in- 
quiry that the plant had not been 
Fic. 4.—Fouquieria splendens: left, not irrigated; right, irrigated. 
irrigated at all, a curious confirmation of the view advanced in this 
paper. 
FOUQUIERIA SPLENDENS (fig. 4)—The non-irrigated specimen 
is growing on the mountain near the Laboratory. The irrigated is 
on the grounds of the Indian Industrial School, Tucson. It has 
received a variable amount of water, more during the past two years 
than formerly. 
PARKINSONIA MICROPHYLLA (fig. 5).—The plant that is not 
irrigated is on the mesa at the northern base of the Laboratory 
mountain. The irrigated specimen is on the campus of the University 
of Arizona and has been irrigated frequently. 
PARKINSONIA TORREYANA (fig. 6).—The non-irrigated palo verde 
is in the draw at the western base of the Laboratory mountain. 
