the Ovula o/" Loi*anthus and Viscum. 77 



7. That the embryo is at first included in the ovulum ; that in Loranthus 

 the funiculus subsequently becomes very short, and the apex of the embryo 

 naked. 



8. That the cotyledons, in some, become subsequently united, except at 

 their bases, and in such two lateral slits are visible externally. 



General Remarks. 



From what has been stated, it will appear that the ovulum is, both in Lo- 

 ranthus and Fiscum, a formation subsequent to impregnation. This remark- 

 able, and, I believe, unparalleled fact, will tend materially to increase the 

 difficulty of understanding or even conjecturing the nature of the first steps in 

 the formation of an embryo. It is evident that it is at total variance with the 

 idea that the ovulum, or female organ, is a nidus adapted to, and necessary 

 for the development of the embryo, which in this view is supposed to be 

 derived entirely and directly from the male. It is needless to add, that it is 

 totally different from the usual development of ovula. 



With respect to the first part of the process of development, I may observe 

 that original continuity of tissue is very general, and perhaps universal. And, 

 in particular, I believe the nucleus of an ovulum to be ab origine solid ; what- 

 ever is produced subsequently in its interior being developed in a cavity formed 

 by an excavating process. 



Although there can be no doubt from its structure and functions, that the 

 fleshy body in which the mature embryo is more or less contained is albumen, 

 yet it may be proper to state in what part of the tissue the necessary change 

 is carried on ; particularly since there is, I believe, no instance of albumen 

 occurring as a primary formation*. 



The albumen in both these genera may, therefore, be classed with those 



* Although I have not proved the existence of a sac in Loranthus, within vehich the tissue which 

 subsequently becomes the albumen, is formed, yet, from the consideration of Viscum, and from the 

 obvious analogy which its 'sac presents to the sac of the amnios in ordinary structures, I have little 

 hesitation in advancing the opinion that the ovulum in Loranthus and Viscum is reduced to its simplest 

 possible state, and that the albumen is a deposit within the tissue of the amnios, the sac of which has 

 at an early period ceased to exist, at least as a distinct membrane. Further researches may hereafter 

 establish the fact of the amnios being the only essential part of an ovulum. 



