96 
Operations were begun at Tucson on February 24th and 
during the following eight days I had the continued assistance of 
Professor J. J. Thornber, whose knowledge of the native flora was 
of the greatest service in the selection of representative material 
of the various species secured, which included the native Cacti, 
I Cereus giganteus (Saguaro) near Tucson, Arizona (see Fig.17). An 
ie tree abent a century old. 
perennial herbs, and shrubs of the region. A systematic ex- 
amination was made of the plantation of Cacti on the University 
grounds and some forms which had not been secured were 
obtained from this collection. 
