226 Mr. Brown on the Female Flower and Fruit o^ Rafflesia Arnoldi, 



tion 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 Phaenogamous plants gene- 

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

 important points different from the description given by M. Mirbel, who con- 

 siders 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 integument 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 perforated 

 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 Phaeno- 

 gamous plants generally, 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*. 



In the more essential points of structure, the ovula of Hydnora and Cytinus 

 agree with that of Rafflesia. They differ, however, in both these genera in 

 retaining their original direction. 



In Hydnora I have ascertained the perforation of the single integument and 



* The earlier production of the inner of the two coats generally present in the ovula of Phaenoga- 

 mous plants, and the absence of the outer in this and several other cases, will probably be considered 

 a valid objection to the terminology of M. Mirbel. 



