IN ORCHIDE.E AND ASCLEPIADEiE. 511
dej30sition of j^ranular matter, becomes the opaque speck or rudiment of the future embryo.
The only appreciable ehanges taking' place in this opacpie rudiment of the embryo are its gradual increase in size, and at length its manifest celhdar structure.
In the ripe state it forms an ovate or nearly spherical body, consisting, as far as I have been able to ascertain, of a uniform cellular tissue covered by a very thin mend)rane, the base of which does not exhibit any indication of original attachment at that point ; while at the apex the remains of the lower shrivelled joints of the cellular thread are still frecpiently visible.
This cellular body may be supposed to constitute the Embryo, which would therefore 1)c without albumen, and whose germinating point, judging from analogy, would be its apex, or that extremity where the cellular thread is found ; and consequently that corresponding with the apex of the nucleus in the unimpregnated ovulum.
T^he description here given of the undivided embryo in Or- chideous plants as forming the whole body of the nucleus, [710 and consequently being destitute of albumen, agrees with the account first I believe published by ]\I. du Petit Thouars,^ and very soon after by the late excellent Richard.^
The only other remark I have to make on the fructifica- tion of this family, is, that the seed itself, as well as its funiculus, is entirely without vessels, and that the funiculus, which in the ripe seed is inserted into the testa close to one side of its open base, can hardly be traced beyond that point.
I shall conclude my observations on Orchideae with a notice of some points of their general structure, which chiefly relate to the cellular tissue.
In each cell of the epidermis of a great part of this family, especially of those with mend)ranaceous leaves, a single circular areola, generally ^ somewhat more opaque than the membrane of the cell, is observable. This areola, which is more or less distinctly granular, is slightly convex,
' Hist, des Orchid, p. 11). = Mem. du Mus. d'lIisL Xa(. iv, p. 41.
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