280 



EXPERIMENTS WITH PLANTS 



155. Method of investigating 

 the entrance of air into the 

 stem by way of the stomata. 



water and exhaust the air (Fig. 

 155). Leaves of Geranium, Mag- 

 nolia, Laurel, etc., may be recom- 

 mended for this experiment. 



Having tried this experiment, 

 perform the following: Fix a leaf 

 or leafy branch air-tight in a cork 

 and insert the latter into a bot- 

 tle brimful of water so as to ex- 

 clude air as much as possible (it 

 will be necessary to insert the 

 point of a knife beside the cork 

 to let the water escape). Hang 

 up the bottle in the sunlight 

 (Fig. 156). The transpiration of 

 the leaves will withdraw water 

 from the bottle, causing a partial 

 vacuum, with the result that air 

 will be drawn in through the 

 leaves and rise in bubbles from 

 the cut end of the stem. The ex- 

 periment shows clearly that the 

 air and the water travel in differ- 

 ent channels in the stem, so that 

 they do not interfere with one 

 another. 



In order to test how far the 

 air penetrates and where it travels 



