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 — of a pollen-tube 
from every grain of the mass. 
Lam 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 of M. Corda; 
which was read before the Imperial Acad. Nature 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 Conifere 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 Coniferz. 
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 
. Cora. . 
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 
