206 Mr, Griffith on the Ovulum of Santalum, 



in L.globosus it may be supposed to have a partial one in the incorporated 

 albuminous part of the embryo-sac. 



The gradation of structure appears to me to be tolerably complete. One 

 modification of Viscuin, in my opinion, tends to show, that in Santalum the first 

 steps towards the disappearance of the usual nucleus take place ; Osyris seems 

 to me to indicate that a similar tendency may affect the embryonary sac ; and 

 Santalum appears to me to allude to a reduction in the embryo-sac to the 

 form of that of Osyris. Nor is this all : Osyris has its albumen and embryo 

 developed outside that end of the sac to which the pollen tubes are applied ; 

 Loranthus bicolor has the same developed outside the opposite end of the sac ; 

 and the partial development of the albumen in the embryo-sac of Loranthus 

 globosus may perhaps be a passage to its development outside that sac in 

 L. bicolor. 



The novel points of structure and development indicated in this paper are, 

 so far as I know, the possibility of the separation of a continuous membra- 

 nous embryo-sac into two distinct parts, of which the lower remains un- 

 changed, though it would almost appear from Osyris to be the most permanent; 

 the presence of the embryo-sac not being necessarily connected with its form- 

 ing one of the constituent parts of the young or of the mature seed ; the 

 longitudinal percursion of the embryo-sac by the pollen tubes; the formation 

 of the albumen, either only partially within the embryo-sac, or almost entirely, 

 if not quite so, without it ; the confluence of the albumina of several sacs into 

 one albumen ; the growth of the embryonic tissues from the continuations of 

 the pollen tubes outside the embryo-sac ; the possibility of one embryo result- 

 ing from a combination of several pollen tubes, and of its becoming interior 

 to the albumen, although it may have been for some time entirely exterior to 

 it. I make no mention of the posterior prolongations of the sacs, in doubt of 

 the true nature or origin of the so-called chalazal apparatus of Thesium ; or 

 of the growth of the embryonic tissues from the ends of the pollen tubes, in 

 doubt of my having misunderstood the observations of M. Schleiden, and in 

 ignorance of those of M. Wydler. 



To the observations on Santalum it may be objected, that the continuity 

 of the vesicle within the apex of the embryo-sac with the tube adhering 

 to its apex, and of the tube with the interior membrane of the pollen grain. 



