104 



THE MICROSCOPE. 



of magnesia, the prismatic form* of which are extremely 

 beautiful when viewed with the polariscope (a). The 

 other forms depicted are those of oxalate of lime, 

 which, it will be seen, assume various shapes (b). When 



occurring in the cells of plants these crystals are fre- 

 quently deposited in a needle-shaped form (raphides), 

 or they may be rectangular or rhombic prisms with 

 pyramidal ends, often forming groups radiating from 

 a centre. The formation of the crystals of silver is a 

 beautiful thing to see. Place a solution of nitrate of 



