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 IN ORCIIIDE.E AND ASCLEPIADEiE. 515

eiico, particularly in the parasitical tribes, of fibrous or spirally striated cells in the parciichyma, especially of the leaves, but also in the white coverin<< of the radical fibres.

In the leaves, they are either short spirally striated cells whose louGfcr diameter is at rii'ht angles to the surface, as in Sfells and FlciirothaUis, and whose fibres or stritC 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, and 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 ]\leyen.^

My concluding observation on Orchideae 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 ceil where they exist these crystals are ar- ranged in a single fasciculus, which is generally of a square form.

The individual crystals, — wdiich 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 auriculee of the column or supposed lateral stamina in Orphydea^, is very remarkable, giving these pro- cesses externally a granular appearance, which has been jis 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.

' Phi/totomie, Uib. 11, f. 1 and 2. - Phj/iotomie.

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