714 Mr. Brown on the Organs and Mode of 



The second point of structure in Orchideee to which I shall 

 at present more briefly advert, is the frequent existence, parti- 

 cularly in the parasitical tribes, of fibrous or spirally striated 

 cells in the parenchyma, especially of the leaves, but also in the 

 white covering 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 Pleurothallis, and whose fibres or striai are connected 

 by a broader membrane ; or, being greatly elongated and run- 

 ning in the direction of the leaf, resemble compound spiral 

 vessels of enormous diameter, and consisting 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 Orchideae relates to the very 

 general existence and great abundance, in this family, of Ra- 

 phides or acicular crystals in almost every part of the cellular 

 tissue. 



In each cell where they exist these crystals are arranged 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 cellular 

 tissue of the auriculae of the column or supposed lateral stamina 

 in Ophrydeae, is very remarkable, giving these processes exter- 



* Phytotomie, tab. 1 1 . f. 1 & 2. 



nally 



