ILLUSTRATIONS. 



PLATES. 



Page. 

 Plate I. Fi^. 1. — One of the larger olive trees on the Bogart-Degolia planta- 

 tion, near Casa Grande, Ariz. Fig. 2. — Olive tree at" Las Palmas," 



near Phoenix, Ariz., after six years of neglect 56 



II. Fig. 1. — View in the olive grove at Florence, Ariz., showing dead 

 apricot and almond trees in contrast with flourishing olives after 

 six years without irrigation. Fig. 2. — Interior view in the grove 

 shown in figure 1, the foliage, on account of crowding, having 

 become thinner than that of the outer row 56 



III. Fig. 1. — View in the Pope olive plantation, near Palm Springs, Cal., 



after six years of neglect. Fig. 2. — One of the larger trees in the 

 Pope olive plantation, showing the low habit of growth of the 

 trees 56 



IV. Fig. 1. — Characteristic burl at the base of an olive tree on the Pope 



plantation, near Palm Springs, Cal. Fig. 2. — Feeding rootlets 



^-^ from 6 inches in depth, on the Pope olive plantation 56 



V. Fig. 1. — Cross section of the midrib of the leaf of Oleaeuropea (Mis- 

 sion variety) . Fig. 2 . — Cross section of one of the apical interned es 



of the stem of Olea europea (Mission variety) 56 



VI. Fig. 1. — View in a 500-acre olive plantation near La Mirada, Cal. 

 Fig. 2. — View in a different part of the plantation shown in 

 figure 1, where the trees have been thinned by removing alternate 

 diagonal rows 56 



TEXT FIGURES. 



Fig. 1. Map showing the points in Arizona and southern California where dry- 

 land olive growth was studied 11 



2. Diagram showing the mean monthly rainfall at Casa Grande, Maricopa, 



Phoenix, and Mesa, Ariz., as presented in Table 1 12 



3. Diagram showing the mean monthly relative humidity at Phoenix, 



Ariz., as presented in Table II 12 



4. Diagram showing the mean monthly rainfall at Palm Springs station, 



Cal., as presented in Table III 19 



5. Diagram showing the relative percentages of fine gravel, coarse sand, 



medium sand, fine sand, very fine sand, silt, and clay in dry-land 

 olive plantations in northern Africa and in Arizona and southern 

 California 21 



6. Olive trees which have died through competition with a row of cotton- 



wood trees on the Pope olive plantation, near Palm Springs, Cal 26 



7. Diagram showing the distribution of superficial roots and deep roots of 



a Manzanillo olive tree on the Pojx' olive plantation 29 



192 7 



