26 ASSIMILATION. [CH. II 



Tropseolum or Clover in small pots, are to be used. The 

 pot is supported in a crystallising glass (G, fig. 5) half filled 

 with soda-lime, which rests on a ground glass plate, and 

 is covered by a tubulated bell-jar, the lower edge of which 

 is ground, but need not be welted. The ground edge is 

 smeared with wax-mixture^, and the junction with the 

 glass plate is made secure by a little embankment of 

 wax-mixture melted into the angle with a hot wire. The 

 aperture of the bell is closed by a rubber cork pierced for 

 the tube T, which contains soda-lime. 



The apparatus should be placed out of doors or in a 

 brightly lighted greenhouse. A control-plant must be 

 fitted up in a similar way except that G may be dispensed 

 with and that T must be filled with sawdust or some 

 indifferent coarsely grained powder. We find that ex- 

 posure from 10 a.m. until the afternoon of the next day 

 gives good results. 



(35) Temperature. 



Elodea or Potamogeton should be deprived of starch 

 by darkness. One portion of the plants should be placed 

 in a glass jar containing about 2000 c.c. of spring water 

 chilled to a temperature of about 5° C. by lumps of ice, 

 the rest in a similar jar kept by meafis of gas regulator 

 at 25° — 30°. The ice will want renewing occasionally 

 during the course of the experiment, which should take 

 place in a bright light and should be continued from 



1 Wax-mixture consists of resin 15 parts, bees-wax 35 parts, vaseline 

 50 parts. The wax and the vaseline are melted together, the resin is 

 powdered, gradually added and stirred. 



