INFLUENCE OF LIGHT UPON ACTION OF STOMATA 
The figures at the bottom of the diagrams indicate the hours from 8 A.M. to 6 P.M. 
The figures at the left are those of the Fahrenheit scale, because our Mason hygrometers 
have only the Fahrenheit thermometers. The other figures to the left of the graphs (in 
parentheses) are the purely arbitrary numerals of the eye-piece micrometer used in measur- 
ing the widths of the stomata. 
Fig. I. Barley, September 16, 1916, age 18 days, bright sunlight, soil very moist. 
Fig. 2. Barley, October 14, 1916, age 24 days, dark foggy morning, light toward noon, 
dull afternoon, 11.3% soil moisture at 9:25 A.M., 10% at 4:30 P.M. 
Fig. 3. Barley, October 7, 1916, age 37 days, dark, cloudy day, light about 2 o'clock 
only, soil very moist at 9:05 A.M., then watered, 21.7% soil moisture at 3:40 P.M. 
Fig. 4. Wheat, September 23, 1916, age 23 days, very bright day, 20.4% soil moisture 
before watering at 8:25 A.M. 
Fig. 5. Wheat, September 24, 1916, age 15 days, bright day, 16.7% at 8:30 A.M., 
watered at 12:25 noon. 
Fig. 6. Wheat, October 14, 1916, age 10 days, dark early, light later, 20.9% soil 
moisture at 9:25 A.M., 22.2% at 4:30 P.M. 
Fig. 7. Oats, September 24, 1916, age 15 days, brilliant day, 9.9% soil moisture at 
8:30 A.M., no water added. 
Fig. 8. Oats, November 11, 1916, age 63 days, bright clear day, 8% soil moisture at 
9:15 A.M., watered and put out of doors in very bright sunshine. 
Fig. 9. Oats, November 11, 1916, age 63 days, bright clear day, 8% soil moisture at 
9:15 A.M., watered and pot left in greenhouse in bright light. 
Fig. 10. Rye, September 23, 1916, age 14 days, bright clear day, 10% soil moisture 
at 9:45 A.M. and not watered later. 
Fig. II. Rye, November 11, 191 6, age 72 days, very bright clear day, 20.9% soil 
moisture, not watered afterwards, plant beginning to bloom. 
Fig. 12. Wheat, October 21, 1916, age 17 days, foggy early, later bright; pot A, kept 
in light, 17.5% soil moisture at 8:45 A.M., watered, 23.7% at 4:00 P.M., difference 6.2%; 
pot B, kept in dark, 30.8% soil moisture at 8:40 A.M., watered at 8:45 A.M., 39.1% at 
4 P.M., difference 8.3%. 
Fig. 13. Wheat, October 22, 1916, age 18 days, light similar to that of preceding day, 
plants the same as preceding (figure 12), treatment exactly reversed, thus: pot B put into 
sunlight, 23.9% soil moisture at 8:40 A.M., watered at 8:40 A.M., very moist all day after- 
wards; pot A, kept in dark after 8:40 A.M., 21.7% soil moisture at 8:40 and then watered. 
Fig. 14. Wheat, oats, rye, and barley, as indicated, December 29, 1916, growing out 
of doors in Experimental Garden since November 4; clear night with heavy frost at 8 A.M., 
light from daylight, sun up at 8:00, light brightest between 11 and 12, following by gradual 
dimming, 17.06% soil moisture. 
Fig. 15. Wild oats, October 14, 1916, bright day, soil very moist; two plants, one 
young, first day after transplanting; one old enough for blooming. 
Fig. 16. Wild oats, November 8, 1916, clear, very bright day with no clouds, 12% 
soil moisture, large plant in full bloom growing in Experimental Garden. 
Fig. 17. Wild oats, November 4, 1916, cloudy with slight rain at intervals, light much 
brighter than could be expected with clouds, etc.; two sets of plants, one young, 4-8 inches 
tall, 12% soil moisture; one large, in bloom, growing in Experimental Garden out of doors^ 
soil moisture 12% before rain. 
Fig. 18. Comparison of cultivated and wild oats, changes in light as indicated by 
symbols at bottom of graph; two sets of plants: cultivated oats, large, about 70 days old, 
24.5% soil moisture; wild oats, large, transplanted from field to greenhouse 35 days earlier, 
15-20% soil moisture. 
