542 ON THE ORGANS AND MODE OF FECUNDATION 



as a continuation of the tissue of the stigma and style, and 

 as existing before the apphcation of the pollen to the 

 female organ. 



And 3rdly, He supposes that the male influence reaches 

 the ovula in Orchidese before the inversion of the nucleus ; 

 an opinion founded, as it seems, on his observations on 

 Epipactis, in which, as well as in some other genera of the 

 order, this is the state of the ovulum in the expanded 

 flower. 



In AscLEPiADEiE M. Brougniart's observations, made 

 chiefly in Asdepias amcena and Gomjyhocarjms fruticosa, 

 accord with my statements as far as relates to the applica- 

 745] tion of the more convex edge of the pollen mass to the 

 base of the stigma, its consequent dehiscence, the protrusion 

 of the pollen tubes, and their penetration into the cavity 

 of the style. 



The chief differences are, 



1st, His not even suspecting the agency of insects in the 

 fecundation of this family, and particularly in the plants 

 examined by him, in which I have regarded their assist- 

 ance as absolutely necessary. 



2ndly, In his assuming that the pollen mass in these 

 two genera of Asclepiadeae is ruptured, and comes in con- 

 tact with the base of the stigma without leaving the cell of 

 the anthera. 



3rdly, His conjecturing that the secretion visible in the 

 expanded flower on the angles of the stigma after removing 

 the glands, is absorbed by the glands and conveyed through 

 their arms or processes to the pollen mass, which it excites 

 to the production of pollen tubes. 



Dr. Ehrenberg, on the subject of Asclepiadeae, repeats, 

 with some slight modifications, his former statements 

 quoted in my paper, and illustrates them by figures. In 

 addition, he suspects that the pollen masses (which with 

 Professor Link he regards as the true anthera, and the 

 cells in which they are lodged as processes of the perigo- 

 nium), are not originally distinct from the glands of the 



