COMMON OBJECTS WORTH EXAMINING. 307 



d. Short Crystal Prisms. — These are cubical crystals, 

 long or short squares, or prisms; indeed all those 

 forms which cannot be classed in the other divisions 

 are placed here. They are usually found in distinct 

 cells, and often also in extensive rows or chains along 

 the veins of leaves, especially in the Leguminosse. 

 They are abundant in the Maple, Linden, white and 

 red clover [Trifdlium ripens, T, frat^nse). Onion, Mon- 

 key-flower {Miniulus ringens), Rabbit's-foot [Trifdlium 

 arv^nse), and many other common plants. 



When the reader is searching for these crystals, a 

 small fragment of the plant should be crushed with a 

 penknife, and examined in water with a moderately high 

 power, as most of the crystals are small. The cuticle 

 should also be stripped off. This may be done in the 

 onion bulb and in the Richweed {Pilea). 



21. Crystals — -If the student has a polariscope he 

 will especially appreciate the beauty of crystals as ex- 

 emplified in color; if he has none he can study and ad- 

 mire the beauty of their forms. Almost any soluble 

 salt may be made to crystallize by preparing a strong 

 solution and allowing it to .evaporate slowly, when the 

 formation of the crystals may be watched with the m'- 

 croscope. A small drop is placed on the slip and 

 allowed to evaporate while on the stage. Sugar 

 crystals may be prepared in this way. Common salt 

 is very easily made to crystallize, and scarcely anything 

 can be more beautiful than salt crystals viewed as 

 opaque objects with a strong light reflected on and 

 from them. The following are also noteworthy: 



Tartaric Acid. — Make a strong solution and place a 

 large drop on the slide. Evaporate with a gentle heat 

 by holding the slide several inches above the top of 

 the lamp-chimney. 



