208 Linnaan Society, 



description of the progress of the development of the embryo, so far 

 as he has been enabled to observe it, in Santalum album, Osyris Ne- 

 palensis, Loranthus bicolor, Loranthus glohosus and two species of 

 Viscum ; each of vrhich subjects is illustrated by an extensive series 

 of microscopical drawings. In connection with these details he pro- 

 ceeds to remark at some length on the four following points : — 1 . the 

 solidity of the ovarium and the appearance of the ovulum after fecun- 

 dation, or rather after the action of the pollen on the stigmatic sur- 

 faces ; 2. the reduction of an ovulum to the nucleus or to the 

 embryonary sac ; 3. the embryonary sac ; and 4. the origin of the 

 embryo. The following is the summary given by him of his ideas 

 of the structure of Santalum, Osyris, Loranthus and Viscum : — 



" In Santalum the ovulum consists of a nucleus and an embryonary 

 sac, prolonged beyond both the apex and base of the nucleus : the 

 albumen and embryo are developed in the parts above the septum 

 [in the exserted portion of the sac] , the parts below and the nucleus 

 remaining unchanged. The embryo is developed from the pollinic 

 vesicle. The seed has no actual proper covering, and no other theo- 

 retical covering than the incorporated upper separable parts of the 

 embryo-sac. 



" In Osyris the ovulum is reduced to a nucleus and an embryonary 

 sac, which is prolonged in the same directions as in Santalum, but not 

 to such a degree beyond the apex of the nucleus. The seed is formed 

 outside the embryo-sac, and is absolutely without proper tegument, 

 or whatever covering it may have did not enter into the composition 

 of the ovulum. The embryo appears to be developed at some di- 

 stance from the anterior end of the pollen tube. 



*' In Viscum the modifications appear to me to be two : in the one 

 an evident cavity exists in the ovarium, and the ovulum appears to be 

 reduced to an embryonary sac hanging from one side of the base^of 

 a nipple-shaped or conical placenta. In the other the ovulum is 

 reduced to an embryonary sac, but this is erect, and has no such ob- 

 viously distinct point of origin as in the first. In both the albumen 

 has no other proper covering than the incorporated embryonary sac ; 

 and, at least in the last, the embryo appears to be a direct transfor- 

 mation of the pollinic vesicle. 



** In Loranthus each ovulum appears to be reduced to an embryonary 

 sac, the albumen is developed either partly within the sac, or entirely, 

 or almost entirely, without it. The embryo is a growth from the 

 ends of the continuations of the pollen tubes outside the anterior 

 ends of the embryo-sacs, and is, in one modification, exemplified by 

 L. glohosus, up to a certain period exterior even to the albumen. In 

 L. bicolor the albumen has no proper tegument ; in L. globosus it 

 may be supposed to have a partial one in the incorporated albumi- 

 nous part of the embryo -sac. 



*',The gradation of structure appears to me to be tolerably complete. 

 One modification of Viscum, in my opinion, tends to show that in San-- 

 talum 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. 



