98 RAPHIDES COMPOSITION. [BOOK i. 



and collected firmly into bundles, which are a little shorter 

 than the cells in which they lie. They are, in most instances, 

 formed in the cells of Merenchym and Parenchym without 

 order ; but Meyen has observed that in the bark of the Way- 

 faring Tree (Viburnum Lantana) they are principally stationed 

 in the interior of thin-sided cells, clustered in cavities of 

 thicker-sided tissue. 



Link compares the Raphides in plants to calculi in animals. 



Raspail wrongly asserts that they are never found either in 

 Cactus or elsewhere in the inside of the bladders of cellular 

 tissue, but are exclusively placed in the intercellular passages. 

 The slender kind (fg. 13.) he states to be crystals of phos- 

 phate of lime, from Vo to -3^-0 of a millemetre in length, and 

 to be in reality six-sided prisms, terminated at each end by 

 a pyramid with the same base. The crystals found in the 

 Cereus and Rhubarb (figs. 11. and 12.), he says are composed 

 of oxalate of lime ; and he represents them to be right-angled 

 prisms, terminating in a four-sided pyramid. (Nouv. Syst. 

 de Ch. Org. p. 522.) According to Marquart the raphides of 

 Aloe arborescens consist of phosphoric acid combined with 

 lime and magnesia. Right rhombic crystals are said to be 

 carbonate of lime ; octahedral crystals, and six-sided prisms, 

 to be sulphate of lime. 



Mohl says that raphides are never six-sided prisms, as Ras- 

 pail asserts ; but that they are right-angled four-sided prisms, 

 which gradually vanish into points ; and he declares that 

 Meyen is right in asserting that the raphides are constantly 

 formed inside the cells, and never in the interstitial passages 

 of cellular tissue (Anat. Palm. p. 28.) ; about which there is 

 now in fact no doubt. In Liparis pendula, in which the 

 tissue is very thin, the raphides may be seen in situ without 

 disturbing the surrounding parts; they there form dense 

 bundles of acicular crystals lying in the centre of cells. 



The same circumstance is particularly visible in the oval 

 cells found in the leaves of Caladium esculentum, Dieffen- 

 bachia Seguina, and some other Arads. Here the acicular 

 raphides are not only collected in bundles inside the cells, 

 but are expelled from them Jby an opening at each end of the 

 cell, on which account Turpin calls such cells Biforines. 



