Oi' THE rXI^EPIlKr.NATKD OVULUM. 449 



from the [)laceiita, tlic ovula arc in reality resiipiiiatc ; an 

 economy apparently essential to their development. 



The distinct origins and diti'erent directions of the 

 nom'ishing vessels and channel throngh which fecunda- [550 

 tion took place in the ovnlum, may still bo seen in many of 

 those ripe seeds that are winged, and either present their 

 margins to the placenta, as in Proteaceae, or have the plane 

 of the wing at right angles to it, as in several Liliace^T. 

 These organs are visible also in some of those seeds that 

 have their testa produced at both ends beyond the inner 

 membrane, as Nepenthes ; a structure which ])roves the 

 outer coat of scobiibrm seeds, as they are called, to be really 

 testa, and not arillus, as it has often been termed. 



The importance of distinguishing between the membranes 

 of the unimprcgnated ovukun and those of the ripe seed, 

 must be sufficiently evident from what has been already 

 stated. But this distinction has been necessarily neglected 

 by two classes of observers. The first consisting of those, 

 among whom are several of the most eminent carpologists, 

 who have regarded the coats of the seed as products of 

 fecundation. The second, of those authors who, professing 

 to give an account of the ovulum itself, have made their 

 observations chiefly, or entirely, on the ripe seed, the coats 

 of which they must consequently have supposed to be 

 formed before impregnation. 



The consideration of the arillus, which is of rare occur- 

 rence, is never complete, and whose development takes 

 place chiefly after fecundation, might here, perhaps, be 

 entirely omitted. It is, however, worthy of remark, that in 

 the early stage of the ovulum, this envelope is in general 

 hardly visible even in those cases where, as in liibbertia 

 volubilis, it attains the greatest size in the ripe seed ; nor 

 does it in any case, with which 1 am accpiainted, cover the 

 foramen of the testa until after fecundation. 



The IcHia, or outei' coat of the seed, is verv 2;encrallv 

 formed by the outer membrane of the ovulum ; and in most 

 cases wliere the nucleus is inverted, which is the more [ssi 

 usual structure, its origin may be satisfactorily determined; 

 either by the hilum being more or less lateral, while tlu^ 



29 



