198 Mr. Griffith on the Ovulum r^j/"Santalum, 



at first suspected was the only part of the embryo (the rest being then funicu- 

 lus), corresponds, I think, in situation with the collet; it is very evidently not 

 the point of the radicle, for this will subsequently be found so close to the 

 vesicle as to authorize me in assuming that the greater part of the soft cellular 

 tissues becomes the body of the root. 



Up to the appearance of the very original memoir of M. Schleiden " on the 

 Development of the Organization in Phsenogamous Plants," with which I am 

 acquainted through a translation in the ' London and Edinburgh Philosophi- 

 cal Magazine' for 1838, our knowledge of the origin of the embryo was by no 

 means definite. My own acquaintance with the subject did not extend beyond 

 the penetration of the nucleus by the pollen tube or tubes to a considerable 

 depth in many instances. So far as I can understand the translation, it 

 would appear that the growth of the embryo must take place from the in- 

 flected end of the embryo-sac. But this certainly does not agree with a 

 subsequent passage, which I have elsewhere quoted, relative to the entrance 

 of the pollen tube into the sac of the embryo, and the gradual conversion of 

 its end directly into the embryo. Nor does it agree with the plates, which 

 correspond with the passage just referred to and with my observations on 

 Santalum, and agree well with those on Loranthus. 



If M. Schleiden is of opinion that in general the boyau penetrates into the 

 ernbryonary sac, and that the embryo is derived from its intruded extremity, as 

 indeed he has delineated it, Santalum and Loranthus become strong corrobora- 

 tions of so grand a doctrine, and Osyrls an exception confirmative of the rule. 



But none of my observations have tended to confirm his idea of the inflec- 

 tion of the embryo-sac before the pollen tube ; and it appears to me sufficiently 

 obvious, that if such were the case, the cylindrical bag constituting the "embryo 

 in itsjirst stage of development" would consist of three membranes or layers: 

 viz. the first or outer, of the ordinary and uninflected membrane of the sac ; 

 the second, of its inflected portion ; the third, of that of the pollen tube itself. 

 It is also worthy of attention that M. Schleiden makes no mention of the 

 ultimate fate of the inflected portion, which in his illustrations is only repre- 

 sented as partial, and precisely such as might be expected to occur during the 

 gradual}} intrusion of a membranous tube into a membranous or membrano- 

 cellular sac. 



