FLOWERING PLANTS 1 29 



guage. The tube is filled with water. Very soon the water 

 descends in the tube and continues to do so rapidly, showing that 

 the plant is using up the water. The cork ought to be covered 

 with parafline so that evaporation from that source can not take 

 place. 



This apparatus may be balanced on a pair of scales, or a pot 

 with a growing plant in it may be thus balanced, and it will soon 

 show loss of weight. (A simple and effective pair of scales may 

 be made by the children of a rod of wood eighteen inches long, 

 strings and two pieces of board six inches square.) To show that 

 the water escapes from the plant by the leaves, allow the leaves 

 to rest on the polished surface of a cold piece of glass or polished 

 steel. 



If this plant, or a plant in a pot is inclosed by a bell-jar or 

 glass shade, the water coming from the plant will be condensed 

 on the sides of the glass. 



To trace the course of the water absorbed by the roots, place 

 a solution of some aniline dye in the water (eosin is good.) The 

 coloring can be traced in the stem, if translucent, and thru the 

 veins of the leaves after some hours or a day. 



These experiments may well be followed by an examination 

 of the epidermis of a leaf with the microscope to see the stomata, 

 the openings thru which the water passes. By tearing the leaf 

 crosswise portions of the thin transparent skin which covers the 

 leaf can be obtained, mounted in water, and the outline of the 

 epidermal cells may be seen. Notice also the curved cells bor- 

 dering and making the stomata. 



Thru these not only does the water go out, but the oxygen 

 sometimes passes out and the carbonic acid passes in (sometimes 

 oxygen comes in). Thus it is seen that thru the root-hairs the 

 water and certain substances dissolved in water, and thru the 

 stomata in the leaves the carbonic acid enter as food. The 

 water passes up thru fibers in the root, from these thru fibers in 



