Origin and Development of the Vegetable Embryo. 53 



creased in size; the tegmen still projects beyond the testa, but 

 the nucleus is covered by both membranes, and has not percep- 

 tibly enlarged. But the granular fluid formerly collected at its 

 upper extremity has become converted into a cell, which is the 

 embryonal vesicle {vesichetta embryonale), and is filled with a 

 similar fluid. 



Another epoch succeeds the withering of the flower. The 

 stigma (or stigmata, for there are three) show by their decay that 

 they are dead. The pollen-mass has already acted upon them ; 

 the pollen-tubes, after having traversed their tissue and that of 

 the style, have become prolonged into the evidently enlarged 

 ovary. The ovule has equally undergone a change ; the tegmen 

 no longer projects beyond the testa ; it is contained within it. 

 The nucleus retains its relative situation within the tegmen, and 

 the embryonal vesicle, which is always adherent to its upper end, 

 exhibits the granular fluid, previously distributed throughout its 

 cavity, collected toward its base. [Prof. Von Mohl, in his trans- 

 lation, here explains that the author, by the apex of the embry- 

 onal vesicle, signifies the end corresponding to the apex of the 

 nucleus ; and by the base, the end hanging free in the nucleus ; 

 an explanation rendered necessary by the anatropous condition 

 of the ovule.] The ovule is now exactly in the condition to re- 

 ceive the influence of the pollen. The pollen-tube enters by the 

 orifice of the testa, and its progress into the interior of this first 

 coat is as visible as though no membrane intervened ; its passage 

 through the canal of the tegmen is not always so clear, for either 

 from an actual narrowing of the canal, or from an optical illusion 

 resulting from the cylindrical form of the cells of the tegmen 

 which bound it, the diameter of the tube appears to be much 

 diminished. But there can be no doubt of its prolongation when 

 its extremity is clearly seen to pass out from the narrow canal of 

 the tegmen and into the cavity of the nucleus. The question 

 now is, does it push back the pre-existing embryonal vesicle in 

 order to enter its cavity ? To this Prof. Amici replies, most de- 

 cidedly, no. The pollen- tube merely comes in contact with the 

 side of the upper part of the embryonal vesicle, and remains ad- 

 herent to it, finally withering and disappearing. The end of the 

 pollen-tube, filled with a greenish and granular fluid, contrasts 

 distinctly with the embryonal vesicle, which in the upper part, 

 where it is in contact with the tube, is filled with a limpid fluid ; 

 while below, where the pollen-tube never reaches, it contains a 

 white granular fluid. This condition of the circumstances, the 

 author says, is so constant, that he can tell at a glance whether 

 an ovule has been fertilized or not. Whenever the embryonal 

 vesicle presented itself with the pollinic appendix just spoken of, 

 he was certain of finding the tube engaged in the coats of the 



