400 EAPHIDES. 



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 ifo'ce-starch are so 

 very minute as to be at once distinguished from any of the 

 preceding. 



293. Deposits of mineral matter in a crystalline condition, 

 known as Raphides, 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 pectus, 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 cells : such 

 bundles are well seen in the cells lying immediately beneath the 

 cuticle of the bulb of the medicinal Squill. It does not apply, 

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

 instead of bundles of minute Needles, single large crystals, octo- 

 hedral or prismatic, are frequently met with ; and the prismatic 

 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 Rhubarb, 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 combined 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 1-1 00th. 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 inter- 

 cellular passages ; the cell-membrane, however, is often so much 

 thinned away as to be scarcely distinguishable. Certain Plants 

 of the Cactus tribe, when aged, have their tissue 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 preservation during transport to pack 

 them in cotton, like jewellery. It is not yet known what office 

 the Raphides fulfil in the economy of the Plant, or whether they 

 are to be considered in any other light than as non-essential 

 results of the Vegetative processes. For as all these processes 

 require the introduction of Mineral Bases from the soil, and them- 

 selves produce Organic Acids in the substance of the plant, it may 

 be surmised that the accidental union of such components will 

 occasion the formation of Raphides wherever such union may occur ; 

 and this view is supported by the fact, that the late Mr. E 

 Quekett succeeded in artificially producing raphides within the cells 



