1905] CANNON—WATER-CONDUCTING SYSTEMS 405 
which there is water several times during the year; not continuously 
as in the other ditch mentioned above. 
at ~ 
“ater Pe RS 
10t irrigated; right, irrigatec 
Fic. 8.—Zizyphus lycioides: left, 
1e non-irrigated plant is on the 
ZIZYPHUS LYCIOIDES (fig. 8).—T! 
he campus 
mesa near Tucson. The irrigated plant is growing on t 
