RAPHIDES. 371 



a nucleus. Although the dimensions of the starch-grains pro- 

 duced by any one species of Plant are by no means constant, yet 

 there is a certain average for each, from which none of them 

 depart very widely ; and by reference to this average, the starch- 

 grains of different plants that yield this product in abundance, 

 may be microscopically distinguished from one another, — a cir- 

 cumstance of considerable importance in commerce. The largest 

 starch-grains in common use are those of the plant (a species of 

 Ganna) known as Tous lea mots; the average diameter of 

 those of the Potato is about the same as the diameter of the 

 smallest of the "tous les mois;" and the size of the ordinary 

 starch-grains of Wheat and of Sago is about the same as that of 

 the smallest grains of potato-starch; whilst the granules of 

 Eice-stavch are so very minute, as to be at once distinguished 

 from any of the preceding. 



230. Deposits of mineral matter in a crystalline condition, 

 known as Baphides, are not unfrequently found in the cells of 

 Plants ; where they are at once brought into view by the use of 

 polarized light. Their designation (derived from ^a^i?, a needle) 

 is very appropriate to one of the most common states in which 

 these bodies present themselves, that, namely, of bundles .of 

 needle-like crystals, lying side by side in the cavity of the cell ; 

 such bundles are well seen in the cells lying immediately beneath 

 the cuticle of the bulb of the medicinal Squill. It does not ap- 

 ply, however, to other forms which are scarcely less abundant ; 

 thus, instead of bundles of minute needles, single large crystals, 

 octohedral or prismatic, are frequently met with ; and the pris- 

 matic crystals are often aggregated in beautiful stellate groups. 

 One of the most common materials of raphides, is oxalate of 

 lime, which is generally found in the stellate form ; and no plant 

 yields these stellate raphides so abundantly as the common Rhu- 

 barb, the best specimens of the dry medicinal root containing as 

 much as 35 per cent, of them. In the cuticle of the bulb of the 

 Onion, the same material occurs under the octohedral or the 

 prismatic form. In other instances, the calcareous base is com- 

 bined with tartaric, citric, or malic acid ; and the acicular raphides 

 are said to consist usually of phosphate of lime. Some raphides 

 are as long as l-40th of an inch, while others measure no more 

 than 1-lOOOth. They occur in all parts of plants, — the wood, 

 pith, bark, root, leaves, stipules, sepals, petals, fruit, and even in 

 the pollen. They are always situated in cells, and not, as some 

 have stated, in the intercellular passages; the cell-membrane, 

 however, is often so much thinned away, as to be scarcely dis- 

 tinguishable. Certain plants of the Cactus tribe, when aged, have 

 their tissues so loaded with raphides as to become quite brittle ; 

 so that when some large specimens of C. senilis, said to be a 

 thousand years old, were sent to Kew Gardens, from South 

 America, some years since, it was found necessary for their pre- 

 servation during transport, to pack them in cotton, like jewelry. 



