THE GYMNCEOIUM. 157 



overspreading its surface in precisely the same way, as is repre- 

 sented in Fig. 59. 



A fully developed ovule, therefore, consists of a conically- 

 shaped nucleus of cells containing a cavity or embryo sac in 

 its interior, with two external coverings. The one s, next the 

 nucleus n, which is first formed, is termed the secundine, the 

 other p, the primine. At the apex of the nucleus, both cover- 

 ings leave an opening which has been termed the foramen or 

 micropyle, (/itixpoj little, TtiT-ri gate), through which the nucleus 

 slightly projects when it is not completely covered. The open- 

 ing or mouth of the primine, ex, is called the exostome, {t^a 

 outside, and dfojua mouth;) that of the secundine end, the en- 

 dostome QvSov within). / is the point where the ovule is 

 attached to the placenta. 



The nucleus and its two external investments have no organic 

 connexion with each other, excepting at the base of the ovule, 

 where vessels pass from one into the other and unite the several 

 parts firmly together. This common point of union is termed 

 the chalaza. 



The ovule is attached to the placenta either directly, when 

 it is said to be sessile, or by means of a prolongation or umbi- 

 lical cord termed the funiculus, {^funis, a cord.) The point 

 where this cord is inserted into the ovule is termed the hilum. 

 The micropyle or foramen is therefore situated at the apex of 

 the ovule, and the chalaza and hilum at its base. 



When all the parts of the ovule develope uniformly, they 

 maintain the same relative position throughout their entire 

 growth, as they had at its commencement. Fig. 60. The 

 chalaza ch, is at the hilum or base of the ovule, and the micro- 

 pyle, m, at its apex or opposite extremity, so that a straight 



14* 



