ANGIOSPERMS. ^^^ 



many Angiosperms at the bottom of the sac by free cell-formation. These cells are 

 called by Hofmeister the ' Antipodal Cells,' but their appearance is inconstant even 

 within a very narrow circle of affinity. They do not participate in the subsequent 

 formation of the permanent endosperm, but are either included in or excluded 

 from it (as INIirabilis, Ranunculaceae, &c.), or are absorbed (as in Crocus and 

 Colchicum). In the first edition of this book I had already expressed the opinion 

 that these cells may be considered as the true equivalent of the endosperm of 

 Gymnosperms. 



In the mass of protoplasm which fills up the apical prominence of the embryo- 

 sac, the bodies are formed by free cell-formation whose impregnation gives rise 

 to the production of the embryo, and which are usually termed the Evihyonic or 

 Germinal Vesicles. In a few cases, as in Rheum imdulatum, only one of these bodies 

 is produced, forming a round primordial cell with a large nucleus and concealed 

 in the narrow apical prominence of the embryo-sac. Since after fertilisation the 

 pro-embryo is at once formed from this cell, and from it the embryo, this prim- 

 ordial cell must at present be looked on as homologous with the oosphere among 

 Cryptogams. But usually two embryonic vesicles are formed side by side in the 

 embryo-sac, and in these cases they are generally not round, but longish, ovoid, 

 or even greatly elongated, mostly with the narrower end closely attached to the cell- 

 wall of the sac, while the other rounded end which contains the nucleus projects free 

 into its cavity. In a few, but not many, genera the two embryonic vesicles are 

 elongated to an unusual length and peculiarly organised, as in Watsonia, Santalum, 

 Gladiolus, Crocus, Zea, Sorghum, &c.^ While the lower free end which contains 

 the nucleus becomes rounded off, and presents the ordinary appearance of a 

 primordial cell, the other end (and this is especially striking in Watsonia and San- 

 talum) projects as a slender tubular or caudate elongation into the micropyle or even 

 beyond it. On this appendage may be observed a distinct longitudinal striation, 

 consisting apparently of cellulose, about the nature of which there is still however 

 some doubt. Schacht considers this striated appendage of the embryonic vesicles 

 to be a special organ, which he calls the Filiform Apparatus, and ascribes to it an 

 intermediate function in the process of impregnation. He states that the two filiform 

 apparatuses project from the perforated apex of the embryo-sac ; while Hofmeister 

 asserts that they are still covered by a protuberance of the sac, and that the striation 

 is a peculiar thickening of this part of the wall of the embryo-sac itself — a view 

 which however appears hardly tenable, at least in the case of Watsonia and Santalum. 

 Only the lower rounded part of each embryonic vesicle acts as an oosphere 

 after the contact of the pollen-tube with the filiform apparatus ; Schacht states that 

 in Santalum both develope as often as only one, so far as to produce an embryo ; 

 usually however one is entirely abortive, and the filiform apparatus takes no part in 

 the development which is brought about by impregnation ; Schacht asserts that in 

 Santalum album they are even separated by a septum which arises in the apex of 

 the embryo-sac. Pringsheim and Strasburger have demonstrated that the filiform 

 apparatus corresponds to the canal-cell in the archegonium of Cryptogams. Accord- 

 ing to this explanadon— which seems to me probable— each of the two embryonic 



Schacht, Jahrb. fdr wiss. Bot. vols. I. and IV ; Hofmeister /. c. vol. VII. p. 675. 



