56 PHYSIOLOG Y. 



gains some heat during respiration. We have also seen in the attempt to 

 grow seedlings in the absence of oxygen that very little growth takes place. 

 But when oxygen is admitted growth takes place rapidly. The process of 

 respiration, then, also sets free energy which is manifested in one direction, 

 by growth. 



133. Respiration in a leafy plant. — We may take a potted plant which 

 has a well-developed leaf surface and place it under a tightly fitting bell jar. 



Under the bell jar there also should be placed a 

 small vessel containing lime water. A similar ap- 

 paratus should be set up, but with no plant, to serve 

 as a check. The experiment must be set up in a 

 room which is not frequented by persons, or the 

 carbon dioxide in the room from respiration will 

 vitiate the experiment. The bell jar containing the 

 plant should be covered with a black cloth to pre- 

 vent carbon assimilation. In the course of ten or 



■•'?' 4 '- t twelve hours, if everything has worked properly, the 

 lest for liberation of car- . . . 



bon dioxide from leafy plant lime water under the jar with the plant will show the 



water in smaller vessel. nml °f carbonate of lime, while the other one will 



(Sachs.) show none. Respiration, therefore, takes place in 



a leafy plant as well as in germinating seeds. 



134. Respiration in fungi. — If several large actively growing mushrooms 

 are accessible, place them in a tall glass jar as described for determining 

 respiration in germinating peas. In the course of twelve hours test with the 

 lighted taper and the lime water. Respiration takes place in fungi as well 

 as in green plants. 



135. Respiration in plants in general. — Respiration is general in all 

 plants, though not universal. There are some exceptions in the lower plants, 

 notably in certain of the bacteria, which can only grow and thrive in the ab- 

 sence of oxygen. 



136. Respiration a breaking-down process. — We have seen that in res- 

 piration the plant absorbs oxygen and gives off carbon dioxide. We should 

 endeavor to note some of the effects of respiration on the plant. Let us 

 take, say, two dozen dry peas, weigh them, soak for 12-24 hours in water, 

 and, in the folds of a cloth kept moist by covering with wet paper or sphag- 

 num, germinate them. When well germinated and before the green color 

 appears dry well in the sun, or with artificial heat, being careful not to burn 

 or scorch them. The aim should be to get them about as dry as the seed 

 were before germination. Now weigh. The germinated seeds weigh less 

 than the dry peas. There has then been a loss of plant substance during 

 respiration. 



137. Detailed result of the above experiment to show that respiration is 

 necessary for growth. — The experiment was started at 9.30 a.m. on July 



