Corda on the Impregnation of Plants. 317 



this family the curious fact, that the application of one portion of 

 the pollen-mass to the stigma causes the production of a pollen-tube 

 from every grain of the mass. 



I am not aware of any important addition to our knowledge on 

 this subject during the interval between the publication of Dr. 

 Brown's paper, and the date of the following memoir oi M. Corda; 

 which was read before the Imperial Acad. Naturae Curiosorum, in 

 Sept. 1834, and published in the Transactions of that society for 

 the year 1835. 



M. Corda inferred, from previous observations, that the pollen- 

 tubes usually extend quite to the mouth of the ovules; consequently 

 it became a highly interesting subject of enquiry to determine their 

 further course. In prosecuting the subject, he was induced to ex- 

 amine the mode of fecundation in the Coniferae or Fir tribe ; in which 

 the naked ovules, impregnated by immediate contact with the pollen, 

 would naturally be supposed to offer great facilities for such investi- 

 gations. The subjoined memoir is accordingly restricted to an ac- 

 count of the development of the ovule, and the mode of impregna- 

 tion in the order Coniferae. 



Although the following translation will, I trust, be found substan- 

 tially to embody the ideas of the author, my very slight acquaintance 

 with the German language offers a sufficient explanation for what- 

 ever errors may have been committed. I was obliged to undertake 

 this labor myself, since no one unacquainted with the structure of the 

 ovule, could properly translate a memoir of this kind, however con- 

 versant with the language in which it is written. 



Contributions to the doctrine of the Impregnation of Plants ; by 

 A. J. C. Corda. 



All our views respecting the impregnation of plants have been 

 entirely remodelled since the discovery of pollen-tubes by Amici ; 

 the former hypotheses having been sufficiently refuted by the curious 

 discoveries of Brongniart, no less than by the assiduous and ingeni- 

 ous researches of Robert Brown. Since the appearance of Robert 

 Brown's writings, and his visit to Germany, the results of his inves- 

 tigations are so generally known, that I consider an historical account 

 of them superfluous ; and will only mention that according to my 

 own knowledge, Robert Brown has traced the pollen-tubes quite 

 to .the placenta ; thus partially confuting the opinion of Brongniart 



