Dylan wrote > Vandeventer and others have provided > insights into vegetation of the past utilizing > packrat middens. They have demonstrated that in > the place of the Sonoran Desert flora around Tucson > now there was pinyon-juniper woodland. This was > only about 8000 years ago. > http://sbsc.wr.usgs.gov/cprs/research/… I heard this talk some years ago at the Huntington - the current suite of lower Sonoran Desert plants only came together about 3,000 years ago, with Cercidium species being the last to advance north from warmer areas. <<<<< Bulb content follows >>>>> We have several bulbs in the lower Sonoran Desert, including what we know as Dichelostemma pulchellum, as well as Hesperocallis undulata. There are also Asclepias and Datura species with undergound storage organs. Leo Martin Phoenix Arizona USA