280 



EXPERIMENTS WITH PLANTS 



t 



155. Method of investigating 

 the entrance of iiir 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- 

 elude 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 i)enetrates and where it travels 



