OF THE UNIMPREGNATED OVULUM. 447 



coats of the oviilum before impregnation;^ and of M. 

 'L\irpin, as to the situation of the micropyle, and its being 

 the cicatrix of a vascular cord. Yet he seems not to admit 

 the function ascribed to it, and asserts that it is in many 

 cases wanting.^ 



The account which I have given of the structure of the 

 vegetable ovulum differs essentially from all those now 

 quoted, and I am not acquainted with any other observa- 

 tions of importance respecting it. 



Of the authors referred to, it may be remarked, that 

 those who have most particularly attended to the ovulum 

 externally, have not always examined it at a sufficiently [sis 

 early period, and have confined themselves to its surface : 

 that those who have most minutely examined its internal 

 structure, have trusted too much to sections merely, and 

 have neglected its appearance externally : and that those 

 who have not at all examined it in the early stage 

 have given the most correct account of its surface. This 

 account was founded on a very hmited observation of ripe 

 seeds, generalized and extended to the unimpregnated ovu- 

 lum, in connexion with an hypothesis then very commonly 

 received : but this hypothesis being soon after abandoned, 

 their statement respecting the ovulum was rejected along 

 with it. I 



In the ovulum of Kingia, the inner membrane, with re-1 

 lation to the external umbilicus, is inverted ; and this, as < 

 I have already observed, though in direct opposition to 

 M. Turpin's account, is the usual structure of the organ. 

 There are, however, several families in each of the two 

 primary divisions of phsenogamous plants, in which the 

 inner membrane, and consequently the nucleus, agrees in 

 direction with the testa. In such cases the external um- 

 bilicus alone affords a certain indication of the position of 

 the future embryo. 



It is an obvious consequence of what has been already 

 stated, that the radicle of the embryo can never point di- 

 rectly to the external umbihcus or hilum, though this is 



Elem. Philos. Bot. p. 338. ' U. p. 340. 



