290 MICROSCOPY FOR BEGIXNERS. 



of the common Rich weed (Pilea pumila\ a semitrans- 

 parent plant growing in moist, shady places. 



c. Long Crystal Prisms. These are long crystals, 

 with angular, prismatic shafts and angular tips. They 

 never occur loosely as do Raphides, but one or two 

 together in the tissue of the plant. They are abundant 

 in the cultivated Gladiolus, Flower-de-luce (Iris versi- 

 color), some of the Asters, Cynthia Virginica, Hawk- 

 weed (Hierdcium), the Thistles (Cirsium\ and others. 



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. They 

 are usually found in distinct cells, and often also in ex- 

 tensive rows or chains along the veins of leaves, espe- 

 cially in the Leguminosse. They are abundant in the 

 Maple, Linden, white and red clover (Trifolium repens, 

 T. pratense), Onion, Monkey-flower (Mimulus ringens), 

 Rabbit's-foot (Trifolium arvense), and many other con> 

 mon plants. 



When searching for these crystals a small fragment of 

 the plant should be crushed with a penknife, and exam- 

 ined 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 

 Richweed (P'dea). 



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 



