STRUCTURE.] DEVELOPMENT OF OVULE. 405 



transverse section is made near the slightly-depressed apex of 

 this integument, an extremely minute perforation or capillary 

 channel, extending to the free apex of the included nucleus, 

 may be observed. This account of the gradual development 

 of the ovulum of Rafflesia, I believe, is in every essential 

 point applicable to Pha3nogamous plants generally, except 

 that here one coat only is developed. It is, however, in some 

 important points different from the description given by 

 M. Mirbel, who considers the nucleus in its earliest state as 

 included in the integuments, which in the next stage open 

 and dilate so as to leave it entirely exposed ; they then, as he 

 supposes, remain quiescent until the nucleus has considerably 

 enlarged, when they again become active and increase in 

 size until they once more completely cover it. While the 

 development, as I have here described it, of the nucleus and 

 its integuments in Rafflesia is going on, another change is at 

 the same time gradually taking place, namely, at first a 

 slight bending, which at last ends in a complete inversion, 

 in the direction of the nucleus and its integument in regard 

 to the placenta, with which, in this advanced stage, the per- 

 forated apex of the latter is nearly or absolutely in contact. 

 In this change of direction, the ovulum of Rafflesia resembles 

 that of the far greater part of Phaenogamous plants : the 

 change, however, is effected in a way which is much less 

 common, the curvature in Rafflesia taking place solely in the 

 upper part of the funiculus, the direction of the inverted 

 ovulum being parallel with, but distinct from, the portion 

 below the curvature ; whereas in Phsenogamous plants gene- 

 rally, the curvature is produced in that part of the funiculus 

 which is connate with the testa or outer integument. For 

 this difference a reason, perhaps, may be assigned; the 

 integument which generally forms the testa or outer coat 

 being in Rafflesia entirely wanting, or only indicated by the 

 remarkable dilatation of the apex of the funiculus." (Linn. 

 Trans., xix. 225.) 



Schleiden's account of the progressive growth of the atropal 

 ovule in Buckwheats (Polygonacese), shows the same pheno- 

 mena : " At a certain distance below the apex of the original 

 protuberance (Brown's papilla) an ideal line may be recog- 



