THE FEMALE FLOWER IN CYCADE.fl AND CONIFEKE. l^.i 



Oil the Structure of the Femnfe Flower in Cycadi'-.e 



and CoNIFERyE. 



I'liat the apex of the nucleus is the point of the ovuhun 

 where impregnation takes phice, is at least highly probable, 

 both from the constancy in the ap[)earance of the embryo 

 at that point, aiul from the very general inversion of the 

 nucleus ; for by this inversion its a[)ex is brought nearly, 

 or absolutely, into contact with that part of the parietes of 

 the ovarium, by which the influence of the ])ollen may be 

 sup})osecl to be conununicated. In several of those families 

 of plants, however, in which the nucleus is not inverted, 

 and the placentae are polyspermoiis, as Cistineao,^ it is diffi- 

 cult to comprehend in what manner this inlluence can [555 

 reach its apex externally, except on the supposition, not 

 hastily to be admitted, of an impregnating aura tilling the 

 cavity of the ovarium ; or by the complete separation of 

 the fecundating tubes from the placentae, which, however, 

 in such cases I have never been able to detect. 



It would entirely remove the doubts that may exist re- 

 specting the point of impregnation, if cases could be pro- 

 duced where the ovarium was either altogether wanting, 

 or so imperfectly formed, that the ovulum itself became 

 directly exposed to the action of the pollen, or its fo villa ; 

 its apex, as well as the orifice of its innnediate covering, 

 being modified and developed to adapt them to this 

 economy. 



But such, I believe, is the real explanation of the struc- 

 ture of Cycadea3, of Coniferae, of Ephedra, and even of 

 Gnetum, of which Thoa of Aublet is a species. 



To this view the most formidable objection would be 

 removed, were it admitted, in conformity with the preceding 

 observations, that the a[)ex of the nucleus, or supposed 



^ Tliis structure of ovulum, iudicaicd l)y lliat of tlie seed, as characterising 

 and deliuiug the limits of Cistinctu (iiamely, Cistus, Ilclianthcmum. Hudsoiiia, 

 and Leehea), I communicated to Dr. Hooker, by whom it is noticed in his 

 Flora Scotica (p. 2S1), j)ublished in 1S21 ; where, iiowevrr, an observation is 

 added respecting Giertner's description of Cistus and Ueliaullieiuum. for which 

 I am not accountable. 



