22 THE MICROSCOPE. 



One of the largest forms of starch-granules is that of 

 tons-. J es-mois ( Canna ) . 



The circulating movement of particles in the cells 

 of certain plants is an extremely interesting sight, and 

 in some can be observed without much difficulty. 

 Those generally selected for exhibiting this phenome- 

 non are Char a nitella and the American weed Ana- 

 charis alsinastrum. The long ribbon-like leaves of 

 Vallisneria spiralis a plant not indigenous in this 

 country, but which may be purchased in Covent 

 Garden and elsewhere show this cyclasis, or circu- 

 latory movement, of chlorophyl particles admirably. 

 You must take a very thin strip or layer from the 

 surface of a youns: leaf, using a sharp knife ; place 

 this upon a glass slide with a drop of water, and cover 

 it with very thin glass, using a power of 300 or 400 

 diameters. The circulating corpuscles will be seen to 

 traverse the cell-walls round and round. Should the 

 circulation stop, you should submit the strip to gentle 

 heat, when it will go on again. The hairs of certain 

 plants exhibit the same phenomenon, such as those 

 of Tradescantia Virginica, the Virginian spider- wort ; 

 Anchusa paniculata, one of the borage family ; the 

 young hairs of the nettle show the same rotation 

 under a very high power. Crystals, or raphides as 

 they are termed, are found in many plants, and are in- 

 teresting microscopic objects. The name " raphides," 

 from the Greek word r aphis, "a needle/' was first 

 applied to crystals having a needle-like form; but it 

 is now used in a general sense to express any crys- 

 talline formation. These bodies are found usually 

 within the cells in almost any part of the plant 

 in the stem, leaves, bark, or pith. In the bulbs of 

 the lily tribe they occur extensively. You can readily 

 see them in the cuticle of the common onion ; strip 

 off a small piece, and view it with a power of 



