W. HOFMEISTER ON THE DEVELOPMENT OF ZOSTERA. 255 



Gronland also supports, although A. de Jussieu*, so long ago 

 as 1838, demonstrated that this is untenable, by comparison 

 with other Monocotyledonous embryos, and explained the organ 

 as a transformation of the plumule (tigelle) of the embryo, with- 

 out however recognizing the leaf-bearing stem as a secondary 

 axis. An unprejudiced examination of the course of develop- 

 ment completely refutes the older view. But even if it were 

 assumed, for the sake of the pretended analogies, that the direc- 

 tion of the main axis of the embryo underwent a division not to 

 be detected by actual observation ; that the cell of the lateral 

 surface of the flattened -ovate cellular body, which gives origin 

 by its cell -multiplication to the leaf-bearing axis, was the twelfth 

 cell of the first degree of the embryo, and that the obtuse end of 

 that cellular mass underneath this cell was the rudiment of the 

 cotyledon, the cotyledon and the next succeeding leaf would 

 be made to stand in one perpendicular line, i. e. the leaf directly 

 over the cotyledon ; a supposition incompatible with the phaeno- 

 mena exhibited in the after-life of Zostera. 



There is no example among all the Dicotyledons of the 

 principal leaf-bearing stem of a plant being an axis of the second 

 rank, the lateral sprout of a leafless primary axis. The develop- 

 ment of the embryo of Tropceolum, which at first sight appears 

 similar to that of Zostera, differs from it most essentially in the 

 circumstance that the portion of the pro-embryo, from the end- 

 cell of which the embryo originates, is in Tropceolum the primary 

 axis, only crowded to one side by the more vigorous development 

 of the peculiar lateral sprout of the pro-embryo f. 



Among the Monocotyledons there is one plant, Ruppia 

 rostellata, resembling Zostera in many characters of its sub- 

 sequent life, which may be compared with the latter, in reference 

 to the characters of the embryo, without straining any point. 

 The ovule of Ruppia agrees in structure with that of Poiamogeton. 

 Like that, it completely resembles the ovule of Zostera in its 

 early development, in attachment, direction and shape (fig.41 a,b}. 

 But that large cell in the interior which becomes the embryo-sac, 

 only displaces a moderate portion of the nucleus before impreg- 

 nation ; the outer layers of cells of the latter persist (fig. 42). As 

 inPotamoaeton, the previously concentrically-shaped ovule begins 



* Ann. des Sc. Nat. 2 ser., Botanique, torn. xi. 

 f See my essay Die En$tehung des Embryo. 



