STRUCTURE.] 



R APHIDES. 



97 



4. Of Raphides, or Crystals. 



Among the tissue are found certain needle-shaped trans- 

 parent bodies, lying either singly or in bundles, and called 

 raphides. They were first discovered by Rafn, who found 

 them in the milky juice of Spurges (Euphorbias), afterwards 

 they were met with by Jurine, in the leaves of the Snow-flake 

 (Leucojum vernum,) and elsewhere ; and they are now well 

 known to all vegetable anatomists. If a common Hyacinth 



is wounded, a considerable discharge of fluid takes place, and 

 in this myriads of slender raphides (fig. 13.) are found float- 

 ing ; or if the skin of the leaf of the Marvel of Peru (Mira- 

 bilis Jalapa) is lifted up, little whitish spots are observable, 

 which are composed of them ; all these are acicular in form, 

 whence their name. In Cereus peruvianus (fig. 11.) they 

 are found in the inside of the bladders of cellular tissue, and, 

 instead of being needle-shaped, have the form of extremely 

 minute conglomerated crystals, which according to Turpin, 

 are rectangular prisms with tetrahedral summits, some with a 

 square, others with an oblong base. Crystals of a similar figure 

 have been remarked by the same observer in Rheum palmatum 

 (fig. 12.); and their presence, according to him, is sufficient to 

 distinguish samples really from China and Turkey from those 

 produced in Europe. The former abound in these crystals, 

 the latter have hardly any. They are insoluble in alcohol, 

 water, and caustic potash, but are dissolved by nitric acid. 



Raphides are found solitary in the cells of Papyrus anti- 

 quorum, Epidendrum elongatum; &c., scattered in consider- 

 able numbers in the cells of the Plantain (Musa paradisiaca), 



VOL. I. H 



