10 STUDIES IN THE VEGETATION OF THE STATE 



the plant house, was nearly equal in intensity to that of 

 Case III and Case IV. The soil moisture was kept at a good 

 growing per cent, usually at from 12 to 25 per cent, physical 

 water. Case II had the direct sunlight shut out. This re- 

 duced the light to less than one-hundredth of that of full 

 noon-day sunlight. Other factors were kept near the nor- 

 mal. Case III was intended to be a xeropbytic chamber but 

 usually it was nearer normal than otherwise. Case IV was 

 regulated so that the air was almost constantly humid. The 

 soil likewise was kept wet, generally with from 20 to 30 per 

 cent of soil water. In another window, in the air of the 

 laboratory, was a plot designated as Lab. in the records. 

 The air of this plot during the time of experimentation was 

 almost constantly deficient in moisture. The averages of 

 temperatures in Case II, Case III, Case IV, and Lab. were 

 about equal. 



In the plant-house, plants were grown under five measured 

 sets of physical factors. Those grown under the full light 

 are designated in the species lists as P. H. These were 

 kept in good growing condition with a soil moisture of from 

 12 to 25 per cent of physical water, P. I, P. II, P. Ill and 

 P. IV were four plots under essentially the same air condi- 

 tions as the P. H. plot, except that the first two were shaded. 

 P. I and P. Ill were kept at a high per cent of physical soil 

 water, 20 to 35 per cent, but P. II and P. IV were kept at a 

 low per cent. 



5. Temp^'rature aiid Humidity. Air temperatures were taken 

 with a psychrometer in the plant-house and with stationary 

 wet and dry bulb thermometers in the plant cases. The 

 relative humidity, was calculated from these readings. The 

 maximum and minimum thermometer was used for record- 

 ing the extremes of temperature in the plant-house. Soil 

 thermometers were kept constantly in one pot in each plot. 

 Readings of all factors were taken three times daily, morn- 

 ing, noon, and evening, at or near 8 a. m., 12 m, and 4 p. M. 

 For convenience in comparing the records with those of the 

 local U. S. Weather Bureau all temperatures are given in 

 Fahrenheit. 



