220 The Plant World. 



leucophaea and Dendographa minor, Plaiygrapha hyPothallina, 

 and Bacidia herrei, which seems to be in process of developing 

 into two species, one a bark dweller and the other living on sand- 

 stone. 



THE POROUS CLAY CUP FOR THE AUTOMATIC 

 WATERING OF PLANTvS. 

 By Lon a. Hawkins. 

 The advantages of a method whereby the moisture supply 

 of a potted plant may automatically be kept approximately 

 uniform during long periods of time are obvious to all who 

 have to grow plants in pots for any purpose. If the daily at- 

 tention necessary to maintain adequate soil moisture for pot- 

 grown plants may be obviated without producing any un- 

 desirable effect upon growth, the method by which this is 

 possible should be very valuable. The best method so far 

 described seems to be that of Livingston, which he exhibited 

 at the Chicago meeting of the American Association for the 

 Advancement of Science, * and the present experiments have 

 been carried out with the view of obtaining a better knowledge 

 of this method. The plants were grown in common garden 

 soil, the cups used were the same as those used by Livingston, 

 and the method of setting up was similar to that recommended 

 bv him. Three plants of Coleus were grown in the self-watered 

 pot for 180 days, and plants of Vicia faba were grown from 

 the seed to the late flowering stage. 



In the experiment with Coleus, three healthy, pot-grown 

 plants were equally spaced around the porous cup, the latter 

 being placed in the center of an 8-inch pot of the usual form, 

 with the top of the cup level with the rim of the pot. The 

 soil was filled in to within a ceitimeter of the rim. The soil 

 surface was covered, to prevent evaporation, with composite 

 modeling clay, and the exterior of the pot was coated with 

 paraffin. Thus, practically no exchange of gases between 

 the interior of the pot and the outside could take place, ex- 

 cepting through the water of the tube and cup and through 

 the plants themselves. The cup was filled with water and closed 



♦Livingston, B. E.. A method for controlling plant moisture. Plant World, 1 1 : 39-40. 1908 



