Fecundation in Orchidea and Asclepiadea. 743 



ture of the ovulum, to which they adhere with considerable 

 firmness*. 



At what period they reach the foramen of the testa, whether 

 before or immediately after the first faint appearance of the nu- 

 cleus, I have not yet been able to determine. That the tubes 

 thus traced to the foramen of the ovulum are of the same nature 

 as those which I have called mucous tubes, and not those di- 

 rectly produced by the pollen, is proved by their exact agree- 

 ment with the former in every respect, except in their being re- 

 markably and irregularly flexuose, apparently from the nume- 

 rous obstacles they have to overcome after leaving the cords and 

 beginning to mix with the ovula; for in the cords themselves, 

 where the course of the tubes is not at all impeded, they are very 

 nearly or altogether straight. 



The two most important facts stated in the present commu- 

 nication are ; Jlrst, the production of tubes not directly emitted 

 from the grains of pollen, but apparently generated by them ; 

 and, secondly, the introduction of one or sometimes more than 

 one of those tubes into the foramen of the ovulum, the point 

 corresponding with the radicle of the future embryo. 



The principal points remaining to be examined, and which we 

 may hope, by careful investigation, to ascertain, are the precise 

 state of the ovulum at the moment of its contact with the tube, 

 and the immediate changes consequent to that contact. 



* Since these additional observations were read, I have found in several other Or- 

 chideae, especially Habenaria viridis and Ophrys apifera, tubes scattered over the sur- 

 face of the placenta, and not unfrequently inserted, in Uke manner, into the apertures 

 of ovula. 



VOL. XVI. 5 c Supple- 



