ff 



of the gaseous reagents is inconsiderable. 



The general arrangement of the apparatus may- 

 be described as follows. The plants are grown in 

 cylindrical tin cans 7 inches (18 cm.) deep and 6 inches 

 (15 cm.) in diameter. These are standard "soldered" 

 cans which can be obtained from the American Can Go. at 

 small cost. All joints are soldered. In the can with 

 the plant are the three porous cups of the auto-irrigator 

 system. G-lass tubes, connected with the two end cups 

 project above the soil and suffice for water supply 

 to the cups and for cleaning, as described below. IRto 

 the top of the tin can, about one half centimeter (.2 

 inch) above the soil there is soldered a tin top per- 

 forated with three holes; one, centrally placed, for the 

 plant stem, and two, toward the periphery, for the con- 

 necting tubes of the auto-irrigator. If necessary the 

 top is split to permit easy insertion of the plant stem 

 through the central hole. This tin top is intended 

 merely to provide mechanical support for the seal about 

 the stem of the plant, which support is necessary if the 

 seal is to withstand the shocks and bendings of the stem 

 incident to wind-movement of the plant, to taking ahold 

 of the can in moving it, and the like. II o attempt is 

 made to solder the tin-top perfectly to the can or to 

 secure an hermetical seal at the soldered joint. The 

 real seal at this joint and about the projecting con- 

 nection tubes for the auto-irrogator is secured by 



