104 RAPHIDES THEIR SITUATION. [HOOK i. 



decomposed, or to take some of the rotten portions which are 

 frequently on its exterior ; and, by examining either of these 

 with the microscope, it will be seen that there are numbers 

 of isolated cells which contain crystals, which cells are five 

 or six times larger than those of the tissue which have none 

 within them ; and, what appears remarkable, the crystals 

 seldom occupy more than a small portion of the cell though 

 it be so dilated, and in the Squill are usually collected at one 

 end, probably by gravitation ; but in the biforines they gene- 

 rally completely fill a small portion of the cell, about its 

 middle, the ends containing none whatever. 



To prove the same fact as regards the conglomerate 

 kind, let a piece of the root of Rhubarb, or a part of the 

 frond of Zamia pungens, be boiled till the cohesion of the 

 tissue be destroyed, when some of the separated cells will 

 exhibit one cluster generally in each ; but the containing 

 cell is not larger than others of the same plant, and at times 

 very little larger than the mass within it. 



There are . some exceptions to Raphides being found 

 constantly in cells, notwithstanding linger' s assertion that 

 they are exclusively found in their interior, and that the 

 vascular bundles have none within them : for they can be 

 observed in the interior of the vessels in the stem of the 

 Grape vine ; and loose in the anthers, mixed with the pollen, 

 in Hemerocallis purpurea, Anigozanthus flavidus, and many 

 other plants ; and they can be observed in the air cavities of 

 many aquatics. 



The interior of the Stem is the most common situation 

 in the herbaceous plants for Raphides, and it used to be 

 considered the only locality ; but the epidermis of the stem 

 of many plants displays thousands, as that of the Trades- 

 cantias, Opuntia crassa, and others. 



The Bark of many trees also contains them; they are 

 readily observed in the layers of the Lime tree bark, of two 

 kinds : also in the barks of Araucaria imbricata, Cascarilla, 

 Cinchona, and various other plants. 



Even the Pith is not destitute of crystals ; for the Grape 

 vine exhibits them in that situation, as does the Lime tree in 

 the medullary rays, which are processes connected with it. 



