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as prominent as possible the new view which Dr. Schleiden 

 has advanced on the act of impregnation in plants. He sup- 

 poses that the course of the pollen tubes from the stigma to 

 the ovule is the general process in the impregnation of Phane- 

 rogamia, and further that one, rarely a greater number, of 

 these tubes penetrate the intercellular passages of the nucleus. 

 The tube which reaches the embryo-sac presses it forwards, 

 indents it, and appears in the form of a cylindrical bag, which 

 forms the commencement of the embryo, which therefore is 

 nothing more than a cell of leaf-parenchyma ingrafted upon 

 the summit of the axis ; consequently it is formed by the 

 membrane of the pollen tube and by the indented embryonal 

 sac. (Much as I value the observations of Dr. Schleiden, 

 and rejoice that many points of vegetable physiology will be 

 considerably advanced by his profound researches to a more 

 rapid solution than otherwise would have been the case, yet I 

 must declare that these statements are not quite correct. The 

 embryo-sac is certainly never indented by the penetrating 

 pollen tube, nay, the embryo is even frequently of considerable 

 size before any trace of an embryo-sac exists. Rep.) In plants 

 which possess several embryos, just as many pollen tubes are 

 present as there are embryos. From these observations, says 

 M. Schleiden, the important consequence proceeds, that the 

 two sexes in plants have been named quite falsely, for each 

 grain of pollen of the nucleus is a new individual, and the 

 embryo-sac on the contrary should be regarded as the prin- 

 ciple which only determines dynamically the organization of 

 the material substratum. 



It will hence be seen that the statements of MM. Corda 

 and Schleiden respecting the plastic processes in impreg- 

 nation in the interior of the ovulum are quite different : the 

 former are, except the penetration of the pollen tube into the 

 nucleus, which was previously observed by Robert Brown, 

 entirely incorrect ; not only does M. Schleiden say so, but 

 Robert Brown also, and I likewise convinced myself of it soon 

 after the publication of the observations ; nay, M. Corda has 

 completely misapprehended the most essential facts in the 

 structure of the ovule previous and subsequent to impregna- 

 tion, notwithstanding the good observations already extant at 

 the time. The question now is, whether the observations of M, 



