RAPHIDES. 



[ 548 ] 



RAPHIDES. 



sively in the stems of herbaceous plants 

 (Monocotyledons in general and Cactaceae); 

 they also occur in the bark and pith of many 

 woody plants (lime, vine); leaves likewise 

 frequently contain them in vast quantity 

 (Araceae, Musaceae, Liliacese, Iridaceae, 

 Polygonaceae) ; also sepals (Orchidaceae, 

 Geraniaceae) ; in the rhubarbs, and also in 

 Umbelliferae, they occur extensively in the 

 roots; and they abound in autumn in the 

 base of the bulbs of the onion and other 

 Liliaceae. 



The form of the needle-shaped raphides 

 is usually that of a square prism, with pyra- 

 midal ends. These ordinarily occur lying 

 parallel in bundles (fig. 619); another com- 



Fig. 619. 



Fig. 620. 



Fig. 619. Parenchymatous cells of the stem of Rumex, 

 contaming bundles of raphides. Magnified 400 diams. 



Fig. 620. Parenchymatous cells of the stem of Beta, 

 with groups of raphides. Magnified 400 diams. 



mon form is that of rectangular or rhombic 

 prisms with obhque or pyramidal ends ; the 

 smaller of these often present themselves in 

 groups radiating from a centre (fig. 620). 

 Prisms of similar or of six-sided forms, octo- 

 hedra, rhombs, &c., also occur solitary or 

 few together (PI. 39. fig. 28), the larger ones 

 sometimes nearly filling the cavity of the 

 cells in which they lie. The cells containing 

 the bundles of acicular raphides in the Ai-acese 

 also contain a viscid sap, which causes them 

 to burst through endosmose when placed in 

 water, and discharge the crystals. Turpin 

 erroneously described these as organs of a 

 special nature, under the name of Biforines. 

 Raphides most frequently consist of oxa- 

 late of Hme, especially in the Cactaceae, 

 Polygonaceae, &c. ; carbonate of Hme seems 

 to stand next in the order of frequency, then 



sulphate and phosphate of Hme. Their 

 composition may be ascertained by the ap- 

 propriate tests for these salts. It is some- 

 times difficult to determine the form accu- 

 rately, on account of the small size; it is 

 found advantageous to mount well-cleaned 

 and partly crushed crystals in Canada balsam, 

 also to view them rolling over in alcohol 

 (Introduction, p. xxix). 



The peculiar crystalline structures called 

 by Weddell cystolithes, occur most abun- 

 dantly in the famiHes of the Urticaceae (in- 

 cluding Moreae) and the Acanthaceae. They 

 ordinarily consist of a stalked, clavate, and 

 globose, or irregular linear body, suspended 

 in a greatly enlarged cell, most frequently 

 situated beneath the epidermis of the leaf 

 (PI. 39. figs. 26, 27); but they also occur in 

 deeper-seated regions. Their nature and 

 development has been followed by several 

 observers, and they are found to consist of a 

 ceHulose matrix with carbonate of lime cry- 

 stallized in a kind of efflorescence upon the 

 surface. They appear to originate by a little 

 papiHa or column of secondary deposit at 

 the upper end of the cell, which increases 

 by successive concentric layers of cellulose 

 applied on the lower surface, leaving a short 

 stalk-like portion, which remains uncovered 

 and also free from the crystals which gradu- 

 ally sprout out from the thickened head. 

 The crystals may be removed by the action 

 of acid, and then the matrix assumes a blue 

 colour with sulphuric acid and iodine. Payen 

 imagined the thicker portion encrusted by 

 the crystals to be composed of numerous 

 cellules, each producing a crystal : this is 

 erroneous. The cystolithes vary in form; 

 the clavate kinds may be best observed 

 in Ficus elastica (PL 39. fig. 27) and 

 other species, in vertical sections of the leaf; 

 globular forms are found in Parietaria offi- 

 cinalis (fig. 26), and the Hop; in species 

 of Pilea they are linear or crescentic, and 

 suspended by the convex edge. 



BiBL. Lindley (and E. Q,\\Gk^tt),Introd. to 

 Botany, 4th ed. i. p. 97 ; Turpin, Ann. des 

 Sc. nat. 2 ser. vi. p. 5 ; Raspail, Chemie or- 

 ganique; Morren, Bull. Acad, de Bruxelles, 

 vi. No. 3; Mey en, Milller's Archiv, 1839. 

 p. 255, Ann. des Sc. nat, 2 ser. xu. p. 257 ; 

 Schleiden, Grundziige, 3rd ed. pp. 168. 341, 

 Principles, pp. 6. 122; Weddell, Ann. des 

 Sc. nat. 4 ser. ii. p. 267 ; Schacht, Beitr. z. 

 Anat. und Phys. 1854. p. 212 ; Unger, Ann. 

 d. Wiener Museum, i. 1844, Anat. und Phys. 

 d. Pfianz. 1855. p. 123; Payen, Mem. sur I. 

 devel. d. vegetaux, Paris, 1844. 



