of the Pollen Granules. 183 



especially after Brongniart's statement in reference to the 

 stigmatic tissue as the proper passage for the pollen tubes, to 

 advance the opinion that they " penetrate the interspaces be- 

 tween the hairs ;" and I would ask, is not the cuticle a barrier 

 to any such penetration ? If the fact be as he supposes,*! con- 

 sider it quite capable of being demonstrated by careful and 

 minute dissection. The formation of pollen tubes is by no 

 means conclusive; for Mr. Hassall has elsewhere said (p. 103) 

 that this occurs " on parts of the flower distant from the 

 stigma." In one case I observed a cluster of pollen granules 

 upon the style, Mith pollen tubes so completely interlaced as 

 to form an entangled mass of flocculent matter ; but none of 

 these tubes seemed to have any intimate connexion with the 

 style. I dare not even assert that they were not produced under 

 the influence of the stigmatic fluid ; for, since the publication of 

 my paper, I have seen that the stigmatic branches ultimately 

 become revolute, and their papillose surfaces are thus brought 

 into contact with the pollen adhering to the style ; but this 

 takes place long after the emission of the pollen, so that it is 

 difficult to regard the evolution of the stigmatic branches as 

 marking the precise time of fecundation. 



Mr. Hassall's intended experiment on the flowers of Cam- 

 panula pyramklalis, interesting as it will be, will not prove 

 that fecundation is not effected by means of the collecting 

 hairs. In opposition to Brongniart, I have shown that they 

 are reall}"^ the recipients of the pollen granules, and that traces 

 of a foramen exist at the extremity of each hair AAhich has 

 performed its function. I cannot suppose that all this singular 

 mechanism is intended merely to astonish the microscopic 

 observer, and the conclusion is to my mind irresistible, that 

 there must be an important relation between this function of 

 the hairs and the fecundation of the plant; and this even if 

 the pollen tubes cannot be traced from the base of the hair to 

 the ovarium. Notwithstanding all that has yet been ad- 

 vanced on the subject, I confess myself to be somewhat scep- 

 tical as to the necessity for the introduction of pollen tubes 

 into the ovarium of any plant. 



I have only to add, that subsequent observations on the 

 flowers of another species. Campanula Rapuncnloicles, confirm 

 what I have already published in the ' Journal of Botany^ on 

 this subject. 



W. Wilson. 



January IS, 1843. 



