ILLUSTRATIONS. 



PLATES. 



Page. 

 Plate I. Fig. 1. — Balanced system containing Opuntia and squash. Figs. 2 



and 3. — Pots sealed with wax, showing Kubanka wheat seedlings 



pushing through the wax seal 12 



II. The simultaneous wilting of plants growing in the same soil mass 38 



TEXT FIGURES. 



Fig. 1. Apparatus for preventing sudden changes in temperature during the 



determinations of the wilting coefficient 13 



2. Apparatus for determining the wilting coefficient for plants with water- 



storage tissues 48 



3. Simple apparatus for determining the wilting coefficient for plants with 



water-storage tissues 49 



"4. Simple apparatus for determining the wilting coefficient for plants 



which have no sharp wilting point 50 



5. Diagram showing construction of knife-edges 50 



6. A convenient counterpoise weight for use in adjusting the balancing 



system 51 



7. Chart showing the linear relationship between the wilting coefficient 



and the moisture equivalent for thirty-five types of soil ranging in 

 texture from sands to the heaviest clays 61 



8. Chart showing the daily moisture determinations in 1-foot sections to a 



depth of 6 feet in a soil on which Kubanka wheat was growing 62 



9. Chart showing the linear relationship between the wilting coefficient 



and physical measurements of the moisture retentiveness of soils 70 



230 



6 



