172 Mr. Griffith on the Ovulum o/"Santalum, 



this paper has been drawn up, have been, with the exception of Viscum, some 

 months in my possession. But I wished particularly to re-examine that genus, 

 and to examine other species of Loranthus than the two on which the remarks 

 concerning that genus have been founded. I could now extend the inquiry 

 to two or three species of a Santalaceous genus closely allied to Osyris, differ- 

 ing chiefly in its quinary flowers and lobed albumen ; to a plant which would 

 belong to the " Genera Santalaceis afBnia ; fructu supero diversa," of the 

 great Mr. Brown's ' Prodromus' ; and I believe to gener^ such as Olax and 

 Ximenia, the aflSnities of which do not appear to me to have been precisely 

 determined. But I am compelled to come to a temporary conclusion of the 

 inquiry, which now requires a determinate knowledge of the origin of the 

 ovulum, or rather of the placentae ; and I reserve the matters, above alluded 

 to, to be added to an account of the Santalacece and the allied families exist- 

 ing in my herbarium. 



§ 1. Santalum. 



My subsequent observations on Santalum have been directed to the follow- 

 ing points, viz. the origin, structure and limits of the embryonary sac ; the 

 relations of the boyaux with its apex ; and the origin of the embryo. 



With regard to the first, I find that the protrusion beyond the apex of 

 the nucleus takes place long before the opening of the flowers or anthers ; 

 that at the earliest periods at which I have been able to ascertain its exist- 

 ence, it presents itself as a membranous tube of nearly equal diameter, the 

 exserted part being rather longer than the ovulum ; and the included part 

 apparently originating from the base of the ovulum, beyond which it does 

 not appear to be extended posteriorly. 



When the flower-bud is half developed, the embryo-sacs will be generally 

 found to have attained nearly their full length in regard to the outside of the 

 placenta ; and with reference to the inside of this organ, they have undergone 

 a remarkable modification, consisting in their extension backwards and up- 

 wards beyond the base of the ovulum towards the axis of the placentae. The 

 apex of the sac appears up to this period to be quite simple. The enlarge- 

 ment of the part near the apex of the nucleus has commenced ; this I have 

 throughout called the bulb or bulbous portion. 



The changes that occur in the sac antecedently to fecundation consist in 



