172 PLANT BIOLOGY 



In case it is possible to equip a room with laboratory tables the 

 following type is suggested. In the first place the laboratory tables 

 should be firmly fixed to the floor, and arranged so that the light 

 comes from the left side, and if possible also from the back of the 

 room. The desk tops should be 30 inches from the floor and 20 

 inches wide, and should be made of maple or other hard wood. The 

 length of each table will of course depend upon the dimensions of 

 the room, but if possible no more than three pupils should be pro- 

 vided for at a single table. Each student should have at least 

 30 inches of the table space. (Fig. 87.) 



" The finish of the laboratory table tops is a matter of importance, 

 since it must be such as to protect the wood from damage, and keep 

 it clean and smooth. Many prefer a black finish, to obtain which the 

 following method gives good results. 



" Make up solutions : 



(1) Copper sulphate (CuS0 4 ) . . . 625 grams 

 Potassium chlorate (KC10 ) . . . 625 grams 

 Water to make 5 liters 



(2) Anilin oil 300 grams 



Hydrochloric acid (HC1) . . , . 450 grams 



Water to make 2500 liters 



" Apply solution (1), followed immediately by (2) several times, 

 until the wood becomes a dark green, allowing the applications to 

 dry each time. The darker the tone reached, the better. The 

 wood must then be washed thoroughly with soap and hot water 

 applied with a brush. This is necessary in order to remove the super- 

 fluous salts. The table is finished with oil and will then be dead 

 black." 1 



The advantages of the dull black finish are these: (1) there is 

 little reflection of light from this kind of surface into the eyes of the 

 pupils; (2) the black surface furnishes an admirable background 

 for many objects of study ; and (3) the tops are not injured by water, 

 acids, or other chemicals. 



Experience has shown that unless the laboratory must be used 



1 From Lloyd and Bigelow's "The Teaching of Biology." 



