VACCINES AND LORANTH ACE^E. 



385 



cies it is erect, not pendulous, this sac is no doubt analogous to the 

 einbyonary sac, or maaibrane of the vitellus of other plants, and is 

 the only essential part of an ovule. 



An additional affinity, corroborating its relation with ProteaceaB, 

 may perhaps be inferred with Santataceae, especially through Viscum. 

 And it must be borne in mind that in Santalacese, the first steps to- 

 wards the siaiplification of the ovule occur, for in Santalum, and 

 probably as M. Brongniart conceives in the other congeners, the de- 

 velopement of the embryo is confined to the erabryonary sac, which 

 is for the chief part protruded beyond the nucleus ! 



The ovary in its earlier stages, is intimately united with the calyx, 

 it is apparently quite solid, and of a homogeneous densely cellular 

 structure. After fecundation, the first change that occurs, is the cen- 

 tral tissue becoming transparent, as well as more lax. In this, to- 

 wards the centre, will be found a cellular body composed of a variable 

 number of superimposed cellules, according to its age, attached by 

 its slenderest portion to the base of the cavity, irregular in form, 

 and formed by dislocation. There is a tendency too, towards separa- 

 tion between the ovary and calyx, not that this ever amounts 

 to absolute distinction, but merely to pointing out of the limits by 

 a difference in form between the tissues. As the embryonary sac 

 (for such I think is its nature) advances. That which subsequently 

 becomes the envelope (in Loranthus Cornaceous) begins to appear 

 in the form of whitish opaque tissue; it is developed from below 

 upwards, and in its advanced state, is at the apex, or where it 

 corresponds to the radicle, very thin. The limits of the ovary 

 subsequently become more defined, and at length that organ be- 

 comes separated from the calyx by viscous tissue, the commence- 

 ment of which is rather early. 



The subsequent developements are easy to be followed, the em- 

 bryo is of early appearance, and is then a circular cellular body ; it is 

 developed of course near the apex of the albumen : which is of a 

 very lax nature at this period. 



It agrees entirely with Viscum as before observed by me, except 

 that the sac is aboriginally erect ; in Loranthus it is certainly pendu- 

 lous. 



The leaves are not altogether abortive, they resemble much the 

 bractea of the flowers, which are always developed in their axillae. 



Y 2 



