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Schleiden on the act of impregnation are correct, and whether 

 we must dismiss in consequence our old views respecting the 

 sexes of plants. I am of opinion (and shall endeavour to prove it 

 in the third volume of my c Physiology') that M. Schleiden's 

 observations have considerably advanced our knowledge re- 

 specting the plastic process in the impregnation of plants; but 

 it will be shown that the old notions of the sexes of plants must 

 be retained as before, even setting entirely aside the formation 

 of bastards, which could not be explained according to the doc- 

 trine that the anther must be considered as a female ovarium. 



We return at present to the consideration of the embryo. 

 Upon its first appearance, says M. Schleiden, the embryo is to 

 be recognized as a membranous cylinder, rounded and closed 

 superiorly, open inferiorly, and filled with organisable matter, 

 which is gradually converted into cells, beginning from above 

 downwards, during which process the cellular nuclei become 

 apparent, which appear at all times to perform a principal part 

 in the formation of cells*. This cylinder M. Schleiden regards 

 as an axile formation, the upper end of which expands into a 

 globe, whence the cotyledons are developed, the apex (that is 

 to say the axis) remaining more or less evidently free, by which 

 it is proved that the axis exists before the leaves. 



The first appearance of the embryo and the formation of 

 its parts is naturally of the highest importance for the mor- 

 phological explanation of the various parts of the grown plant : 



* With respect to the function of the cellular nucleus several important 

 discoveries have been made in the current year (1838), which in many 

 cases perfectly explain the formation of the cellular tissue of plants. I have 

 also observed in many cases that the cellular nucleus makes its appearance 

 originally as a simple globular mucous cell provided with a solid spherical 

 nucleus, and only at a subsequent period is converted into the disc-like forma- 

 tion which is very frequently attached by excessively delicate, and at times 

 also ramified threads to the inner surface of the cell. From the substance 

 of this disc, the first rudiments (the nuclei) of the amylum globules and of 

 the other cellular sap globules, which for some time adhere to the disc and 

 form a circle around the more solid nucleus, are formed. Subsequently the 

 mucous substance of the disc disappears, the starch globules, &c. increase in 

 size and still remain for some time in that circular position, in which the 

 green cellular sap globules are frequently found in the cells of the epi- 

 dermis. In very young potatoes and in some species of Cactus I have been 

 able to follow up this formation. Rep. [Dr. Meyen here evidently alludes 

 to M. Schleiden's admirable memoir on Phytogenesis, which at present oc- 

 cupies so much of the attention of continental botanists, and of which an 

 English translation appeared in the 6th Part of Taylor's Scientific Memoirs. 

 W. F.] 



