420 



THE MICROSCOPE. 



ducts seen near it in fig. 200. In the section from the India-rubber 

 tree, fig. 199, a network of these lactiferous tubes may be found filled 

 with a brownish or granular matter j that in fig. 200 is an enlarged 

 view of this tissue from the liber of an exogen, taken near the root. 



Among the cell-contents of some plants we have beautiful crystals 

 known as Raphides: the term is derived from patpiQ, a needle; the 

 crystals, when first noticed, were of this shape. They are composed of 

 the phosphate and oxalate of lime ; their use in the economy of the 

 plant is unknown. " Whether the result of chemical affinity, or of a 

 vital process, cannot be decided j but it is certain that they can be 

 produced artificially in the tissue of plants." 



The French philosopher, Geoffrey St. Hilaire, has endeavoured 

 to prove that crystals are the possible transition of the inorganic 

 to organic matter. Crystals have naturally been supposed to conceal 

 the first beginnings of the phase na*med organic, because in crystals 

 we first meet with determinate form as a constituent element. The 

 matter named inorganic has no determinate form ; but a crystal is 

 matter arranged in a particular and essential form. The differences, 

 however, between the highest form of crystal and the lowest form of 

 organic life known a simple reproductive cell are so manifold and 

 striking, that the attempt to make crystals the bridge over which in- 

 organic matter passes into the organic is almost universally regarded 

 as futile. 



1 fig. 201. 2 



1. A Section from the outer layer of the bulb of an Onion, showing a crystal of oxalate 

 of lime, with raphides. 2. A vertical section of root of a Fern. 



If we examine a portion of the layers of an onion, fig. 201, or 

 take a thin section of the stem or root of the garden rhubarb, fig. 202, 

 No. 4, we shall observe many cells in which either bundles of needle- 

 shaped crystals or masses of a stellate form occur. 



Kaphides were first noticed by Malpighi in Opuntia, and were 

 subsequently described by Jurine and Raspail. According to the 



