Porous Clay Cvv for Automatic Watering. 



221 



with a rubber stopper bearing a bent glass tube, this in turn 

 being connected with the water reservoir by means of rubber 

 tubing. The cup was filled while the reservoir was at a higher 

 level, a stream of water flowing through the tube at the time 

 of the insertion of the stopper. The reservoir was placed at 

 various levels below the pot and weights of the latter with 



the plants were taken at inter- 

 vals until it was found that with 

 a water column of 50 cm., the 

 fluctuations in weight were very 

 slight. Then the reservoir was 

 allowed to remain so that when 

 filled the water surface therein 

 was 50 cm., below the bottom of 

 the pot. The arrangem.ent is 

 shown in Fig. 1. 



This experiment began Nov. 

 !9, 1909, and the plants were 

 under observation till May 18, 

 throughout a period of 180 days. 

 During this tim.e they received 

 no water excepting through the 

 cup. During the first ten days, 

 with the reservoir but ten centi- 

 meters below the pot, 395 cc. of 

 water were removed from the 

 reservoir by the auto.matic ap- 

 paratus, and the weight of pot 

 and plants showed an increase 

 of 165 g. Thus about 230 g. 

 had been lost, mainly by trans- 

 piration. On April 13, after 145 

 days, the weight showed a loss 

 of 20 g. since the beginning, al- 

 though the plants had grown con- 

 siderably. This indicates that 



this 



Figure 1. 



date than at the start. 



the soil was slightly drier at 

 During this period several rec- 



ords were lost, and it is impossible to state just what was the 



