Apr. 3-sept. 25. 1916 Illustrations xvil 



Page 

 Plate XCIII. — Chamber with part of outer covering removed: -4 , Double metal 

 wall chamber. B, Heat-insulating outer cover. C, Window to chamber. 

 D, Outlet providing passage for pipes, wires, etc., through the walls of the 

 chamber. The exterior ends of the resistance thermometers for ingoing and 

 outgoing water are seen projecting from the outlet. E, Removable top of 

 chamber. F, Device for heating the air entering the respiration chamber. 

 G, Small pipe carrying water for cooling the outer metal wall of the chamber. 



H, Electric-resistance wire carrying current for heating the outer wall 720 



Plate XCIV. — Apparatus connected with the respiration calorimeter: A, 

 Tension equalizer. B, Mixing bottle for equalizing the temperature of 

 water entering the heat absorber. C, Device for heating air entering the 

 respiration chamber. D, Preheater, and E, final heater, for raising the 

 temperature of water entering the heat absorbers. There is an electric- 

 heating coil in the lower half and an electric-resistance thermometer in the 

 upper half of the final heater. F, Temperature indicator comprising part 

 of the apparatus for controlling the temperature of the water entering the 

 heat absorber. G, Multiple-point switch for connecting the resistance 

 thermometers for the metal walls and air of the chamber with the Wheat- 

 stone bridge for measuring their temperatures. H, Tube conducting air 

 from the respiration chamber to the rotary air pump. /, Tube conducting 



air from the purifying devices to the respiration chamber 720 



Plate XCV. — Devices for controlling and recording temperatures: A, Mechan- 

 ism for shifting the contact on the rheostats controlling the current for heat- 

 ing the outer walls of the calorimeter chamber and the ingoing air. B, Ratio 

 coils for the four bridges governing the action of the shifting mechanism A 

 are combined in this box, together with means for checking the constancy of 

 the resistance of the coils and for correcting slight inequalities in them and 

 also to compensate for small differences in the pair of resistance thermome- 

 ters forming the other arms of each bridge. C, Mechanism for shifting the 

 contact on the rheostat controlling the current in the heating coil in the 

 final heater, shown at E in Plate XCIV. D, Temperature-difference 

 recorder (self-balancing Wheatstone bridge) for continuously recording the 

 difference between the temperature of the water entering and that leaving 

 the heat absorber. E, " Check box" containing the ratio coils of the bridge 

 for temperature difference measurements and coils for extending the range 

 of differences measured, with means for checking the constancy of the resis- 

 tances of the coils and the accuracy of the recorder readings and also for 

 compensating for slight differences in the resistance of the thermometer 

 coils when they are at the same temperature 720 



Mottle-Leaf of Citrus Trees in Relation to Soil Conditions 



Plate H. — Various stages in mottle-leaf of the orange 740 



Plate XCVI. — Orange leaves showing mottle-leaf 740 



Plate XCVII. — A more advanced stage of mottle-leaf of orange, showing the 



reduction in the size of the leaves 740 



Vegetative Succession Under Irrigation 



Plate XCVIII.— Rock Creek Valley, near Rock River Station 760 



Plate XCIX. — A nearer view of the bench slope; the same tree shown in Plate 



C, figure 1 760 



Plate C. Fig. i. — Where upland and lowland meet. Fig. 2. — Characteristic 

 draw; the stream valley beyond. Lupin, wheat-grass, white sage, and 

 gaillardia in the foreground 760 



