EECEEATIVE SCIENCE. 



245 



on some two or three in particular, a small 

 portion of muriatic acid is to be added by 

 means of a glass rod. The raphides will be 

 seen to lose their sharpness of outline, to be- 

 come evidently altered, and in place of the 

 bristling mass of crystals, a little lump of 

 soft, structureless, vegetable material is left, 

 proving the simultaneous deposition, atom 

 for atom, of the organic and inorganic con- 

 stituents. On this interesting fact, Mr. 

 E-ainey's recent researches* have thrown 

 quite a new light. In a beautiful section of 

 rliubarb-root, made by our friend, Mr. H. B. 

 Brady, of Newcastle, the deposition of crys- 

 tals in organic matter contained in the cells 

 is very evident. 



Another modification of raphides is met 

 with in hemp, and many other plants of the 

 nettle tribe {UrticacecB), the mulberries, the 

 India-rubber tree {Fictis elastica), and some 

 others. These are called Cystolithes. "When 

 viewed as opaque they are very beautiful, 

 and are not uncommon in cabinets of micro- 

 scopic objects. No idea, however, can be 

 formed of their true nature when seen in this 

 condition. To understand how and where 

 they are formed, let us take a leaf of pellitory 

 of the wall {Farietaria officinalis), and make 

 a vertical section (Fig. 4) ; we shall then find, 



Fig. 4. — Vertical Seotion of Leaf of Pellitory, show- 

 ing Cystolithe in situ. 



amongst the ordinary tissue of the upper 

 surface of the leaf, large cells, each of which 

 contains a rounded, crystalline mass, de- 



* " On the Formation of Bone, Shell, etc." 8vo. 

 Churchill. 



pendent by a slender thread, of mucous ma- 

 terial, from the \ipper wall of the cell. In 

 the hemp, such occur on both sides of the 

 leaf. 



As to form, it may be briefly said that 

 they are mostly four-sided prisms, terminated 

 by pyramids, the section square or lozenge- 

 shaped ; octohedra sometimes occur, as may 

 be seen in the pulpy portion of an orange. 

 In their composition, lime is the chief base, 

 united with oxalic, phosphoric, malic, citric, 

 or tartaric acids. " The watery fluids tra- 

 versing the tissues of growing plants, in con- 

 sequence of evaporation from the leaves, and 

 the continual absorption by the roots, neces- 

 sarily contain various inorganic salts dis- 

 solved in them. Moreover, certain organic 

 acids, such as malic, tartaric, etc., are always 

 formed in the processes of vegetable diges- 

 tion. All these substances and their com- 

 pounds arc, for the most part," dissolved in 

 the cell-sap,"* but by miitual reaction thej' 

 become precipitated in the crystalline form. 

 For purposes of isolation, it may be, a deli- 

 cate layer of protoplastic substance is then 

 thrown round them. They are most abundant 

 in the autumn. The vital powers, through 

 the heats of summer, have kept the materials 

 composing them in a state of solution ; but 

 these receive a check, the delicate balance is 

 upset, and chemical affinities now assert their 

 supremacy by the formation of myriads of 

 crystals. This view is confirmed by some 

 very interesting experiments, made a few 

 years ago by Mr. Edwin Quekett, to show 

 the possibility of their formation by artificial 

 means. He saturated rice-paper with lime 

 by repeated soakings in lime-water, and then 

 placed portions in weak solutions of oxalic 

 and phosphoric acids. From the former, 

 masses of conglomerate raphides, precisely 

 like those of rhubarb, were procured. In 

 the cells of the latter were a few rhomboidal 

 crystals. The conditions regulating develop- 



* Henfrey, " Elementary Course of Botany." 



