LIST OF PLATES. 
PLATE 13. Map of Desert Laboratory domain, showing distribution of Encelia 
PORE DIGD Gea ee RN tise 4.5 xa he gas ss pia pry oi atin we eee oe 
PLATE 14. Map of Desert Laboratory domain, showing distribution of Larrea 
tridentai® Over an area Of dbout 1,800 acres. 2... 6. eek ee enews 
PLATE 15. Map showing distribution of sahuaro (giant cactus) on the Tumamoc 
Pana eeieiiie ye CGO, ATIZ0NA .. . 0c. cc 4k ahaa beep Wh ee chee 
PLATE 16. Map of West part of Laboratory domain with land adjacent on the 
North and South, showing physiographic and soil areas and distribution 
of Cereus giganteus. Area 700 acres. May, 1907. ‘Total number of 
Poetical MlaOts Ol SIAR CACt~AS, SIF. i. ene Oe ee nes Bai a 
PLATE 17. Map showing distribution of Cercidium torreyanum on West part of 
Laboratory domain and vicinity, Tucson, Arizona. November, 1907. 
Rea OC GEG i ET ae tend aS ete ne Sl ee a SG At cack 9 phe ee tes ee 
PLATE 18. Desert Laboratory domain and vicinity, showing approximate distri- 
bution of Prosopis velutina over an area of about 1,800 acres 
PLATE 19. Soil map of a part of Solomonsville sheet, Arizolia «eee en 
PLATE 20. Desert Laboratory domain and vicinity, showing i invasion of Ei enue 
cicutartum. ‘The numbered patches show the position of areas occu- 
pied by alfilaria, in February, 1906 
ae eee eee ere eran ce tea ik  e AUR GAS Ueaapetain ade DSP Ve She aceal mar een ove 
Permanently marked area No. 7, showing invasion of Erodiwm cicutarium. 
In center of area a large individual of Parkinsonia microphylla. 
Anchoring roots of a sahuaro measuring 6.8 meters high and 39 cm. in diam 
eter at the base. 
PLATE 22. Desert Laboratory domain and vicinity, showing invasion of Hordeum 
murinum. ‘The numbered patches show the position of areas occupied 
PONS AI eT QOL Wi preteen Pmt ole cena wip needa gk cinee nce aioe ttt akan acinar de 
PLATE 23. Curve showing expansion and contraction of sahuaro (Cereus gigan- 
teus) from March 3, 1906, to May 26, 1907. Precipitation is indicated 
jay ean Ser vA Fans Cte babe yn an este, Buran eeoee, PA aes ea eee es a we 
PLATE 24. Chart of the root-system of sahuaro (solid lines), creosote-bush 
(jotted lines), and Pariinsonta (broken lines). .... 20. ase ive oe ee 
ED ees eG eee i Ms Schad 2 vlata sh orate oe Wales le doe, fae eign bl « Weauan Y wae 
Cucopa Mountains at western margin of Colorado Delta. 
Volcanic hills in Great Basin, near Hazen, Nevada. 
Typical slope West end of Santa Catalina Mountains from the North. 
PLATE 26. Reservation and vicinity of the Desert Botanical Laboratory of Tuc- 
fon MAtizone ourveyed OCCtOber, TQ00 nt. ae suede be es ke toe 
PLATE 27. Geological map Tumamoc Hills and vicinity Tucson, Arizona...... 
Prateerss Crves.0);sol-miorsttire, | winamoc Hilla.) i. neces wen eae 
iPUATE 208 Curves of soll-moisture, Larrea Slope... 0. ea ce eee ey es 
PLATE 30. Curves of soil-moisture, WLS) Od ec ade tee OM oe Bah tea eae 
PrAate 31. Curves of soil-moisture, Santa Cruz plain. ..- 26. 6124s, os or eee es 
Cle, ee 6 le. a) fe) vl 6, B16 6) We 6 Ose wl ce) a) ie OL Whe) we Oak Cele im 
