261 



The first two species occur throughout the United States 



and Canada, the last species does not occur in the United 



States or Canada, but is found in the West Indies and Mexico. 



Purdue University, 

 Lafayette, Indiana 



ANOTHER RESPIRATION EXPERIMENT 



By Jean Broadhurst 



For two years we have been using the following device for 

 showing that green plants give out CO2. Many methods have 

 already been described; this is added only because it is so easily 

 put up and because the contrast with the control is most marked. 

 An air-tight joint made with w^ater is more certain than when 

 made with vaseline, etc.; it is also less "mussy." 



A dish. A, is partly filled with water. In it are placed a glass 

 vessel for lime (or barium) water, B, supported on any solid 

 support, C, to raise it above the water in ^. A leaf (geranium) 

 may be placed over B with the petiole extending into the water 



■ vc - ^ ->^. w ^ nrr^r^-grs^ £ 



Fig. I. — A, a dish or pan containing water for making an air-tight joint around E. 



B, glass containing lime-water. 



C, support. 



D, a geranium leaf. 



E, a glass dish enclosing D and B. 



in A. (The petiole is, of course, not necessary, but students 

 seem to feel that the conditions are more normal when the petiole 

 has access to water in this way.) Over all is inverted a crystal- 

 lizing dish, E, which should be but slightly wider in diameter than 



