IN ORCHIDEiE AND ASCLEPIADEiE. 511 



deposition of granular matter, becomes the opaque speck 

 or rudiment of the future embryo. 



The only appreciable changes taking place in this opaque 

 rudiment of the embryo are its gradual increase in size, and 

 at length its manifest cellular 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 membrane, 

 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 

 frequently visible. 



This cellular body may be supposed to constitute the 

 Embryo, which would therefore be 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. 



The description here given of the undivided embryo in Or- 

 chideous plants as forming the whole body of the nucleus, [7io 

 and consequently being destitute of albumen, agrees with the 

 account first I believe published by M. 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 Orchidese 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 membranaceous 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. 19. ' Mem. du Mus. d'Hisl. Nat. iv, p. 41. 



