IN ORCHIDE^ AND ASCLEPIADE^. 515 



encCj particularly in the parasitical tribes, of fibrous or 

 spirally striated cells in the parenchyma, especially of the 

 leaves, but also in the white coverina; of the radical fibres. 



In the leaves, they are either short spirally striated cells 

 whose longer diameter is at right angles to the surface, as 

 in Stelis and PleuroiJiallis, and whose fibres or striae are 

 connected by a broader membrane ; or, being greatly 

 elongated and running in the direction of the leaf, resemble 

 compound spiral vessels of enormous diameter, aud consist- 

 ing entirely of the spiral fibres with no visible connecting 

 membrane : the real spiral vessels in the same species 

 being, as they generally are in the family, very slender and 

 simple. In' the white covering of the radical fibres the 

 shorter striated cell is met with in many genera, especially 

 I think in Oncidium and Epidendrum, in one species of 

 which they have been remarked and figured by Meyen.^ 



My concluding observation on Orchidese relates to the 

 very general existence and great abundance, in this family, 

 of Raphides or acicular crystals in almost every part of the 

 cellular tissue. 



In each cell where they exist these crystals are ar- 

 ranged in a single fasciculus, which is generally of a square 

 form. 



The individual crystals, — ^which are parallel to each 

 other, — are cylindrical, with no apparent angles, and have 

 short and equally pointed extremities. 



The abundance of these fasciculi of crystals in the cellu- 

 lar tissue of the auriculae of the column or supposed lateral 

 stamina in Orphydeae, is very remarkable, giving these pro- 

 cesses externally a granular appearance, which has been pis 

 noticed though its cause seems to have been overlooked. 



In the recent work of Meyen,^ also, some examples of 

 these crystals in Orchideae are given. 



' Phytotomie, tab. 11, f. 1 and 2. ^ Phytoiomie. 



