T905] CANNON—WATER-CONDUCTING SYSTEMS 401 
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Not irrigated | Irrigated Semi-irrigated 
Fic. 1.—Acacia Greggii: left, not irrigated; right, irrigated. 
The following outline indicates some of the conditions of growth 
of the plants studied. 
Acacia Grecct (fig. r).—The non-irrigated specimen was taken 
by the roadside between an old and at present unused irrigating 
ditch and the road ditch. Water stands in the latter for a consider- 
able period after each heavy rain, and thus the effects of the rain are 
conside ‘rably prolonged. The irrigated form was growing about 
6™ from a ditch in which the water flows the most or perhaps all of 
the year. The older portion of the silent cain’ stem does not 
4 The ducts of the irrigated plants were very small; see figs. 5, 0, 7: 
