364 Dr. L. Radlkofer on Fecundation in the Vegetable Kingdom* 



My last-year's observations on various plants, and some which I 

 have just completed on the unfecundated embryo-sac of Fiscum, 

 have taught me that the germinal vesicle by no means possesses so 

 firm a cell-membrane as we are accustomed to see in completely- 

 developed vegetable tissues ; that it has sufficient solidity to retain 

 its original oval form for a few moments when the section passing 

 through, halves both embryo-sac and germinal vesicle ; but very soon, 

 directly the contents of the latter begin to coagulate under the 

 influence of water, it shrivels up, follows the contracting contents, 

 and can no longer be perceived as distinct from them. In other 

 words, the coagulating cell-contents do not retract from the cell-wall, 

 but remain constantly in intimate contact with it, the cell-wall 

 coagulating equally with the contents. But that we have not here 

 to do with a mere primordial utricle, with a naked cell, is shown by 

 the following conditions : — If we take a portion of the embryo-sac 

 of Viscum album consisting of about ^th of its length, and turn this 

 inside out, so that the germinal vesicles lie outside and are seen free, 

 with no membranous portion of the embryo-sac lying over or under 

 them to obscure the view, — and then carefully tear them with a 

 needle, supposing this has not already happened in the previous 

 manipulation, — their membrane remains as an extremely delicatey 

 raggedy and wrinkled pellicle adhering to the everted inner surface 

 of the embryo-sac. It is of unequal thickness — thicker at the base 

 of the germinal vesicle, thinner at its apex. At the exact place 

 where it passes off, free (as side- wall), from the basilar surface of the 

 germinal vesicle, its surface of attachment to the embryo- sac, its 

 optical section appears as a broad line with a double boundary, under 

 a power of 160 diameters. Towards the apex of the germinal vesicle 

 (turned away from the top of the embryo-sac) the membrane becomes 

 thinner and thinner, until, at the very top, it is, in its earlier stages, 

 a scarcely consolidated pellicle. If the germinal vesicle had not a 

 proper membrane, of appreciable thickness at least at the base, the 

 boundary-line of its surface of attachment to the embryo-sac could 

 not present itself as double, which is the case here in Viscum, even 

 under a low magnifying power. Henfrey's observations were made 

 on flowers which had been long preserved in spirit : the germinal 

 vesicles must here naturally have been contracted, and could no 

 longer present a distinct cell-membrane. I shall discuss in the sequel 

 Henfrey's view as to the occurrence of conjugation between the 

 embryo-sac and the pollen-tube. 



London, June 8, 1856. 



[Note by Translator. — The remarks in the preceding paragraphs are by 

 no means convincing. It is our universal experience of nascent cells, that 

 the cellulose membrane, be it ever so thin, does not contract on the con- 

 tents ; on the contrary, it is always first somewhat expanded through endos- 

 mose, and leaves the contents^ afterwards shrinking again (evenly), which 

 is admissible by its elasticity ; by that time, however, the contents have 

 shrunk up and coagulated, so that they lie free permanently in the cavity 

 of the cell.— Since the above notices were written, Schacht has published 



