5i6 



PHANEROGAMS. 



apex of the stem exists for the present only as the end of the longitudinal axis of 

 the embryo; an elevated piece of tissue, the vegetative cone of the stem, is not 

 formed till later deeply enclosed between the cotyledons. The posterior or basal 

 end of the axis of the embryo after the differentiation of its primary meristem 

 into dermatogen, periblem, and plerome (//, ///, IV), is, so to speak, open as 

 long as this differentiation has not also taken place in the hypophysis (/z) ; but 

 finally it takes place in it also and in such a way (as is shown in Fig. 372, V), that 



ff 1 



Fig 372.— Formation of the embryo of Cap^elld Bursa-pastOyis (after Hanstein) ; I— VI various stages of development, 

 Vb apex of the root seen from below; i, i, z, 2, the first divisions of the apical cell of the pro-embryo (suspensor), 

 h h the hypophysis, u the pro-embryo, c the cotyledons, s apex of the axis, w root (the dermatogen and plerome are 

 shaded dark). 



the upper of its two cells breaks up into two layers [K), the outer of which becomes 

 continuous with the dermatogen of the axis, while the inner layer forms a pro- 

 longation of the internal axial tissue. The low^r cell of the hypophysis {h) divides 

 cross-wise {V h, seen from below) and may be regarded as a transitional structure 

 between pro-embryo and root (appendage of the root) or as the first layer of the 

 root-cap. Hanstein's description of the growth of the root-cap of Phanerogams, 

 confirmed by Reinke\ is of very great value, showing, as may be seen from 



» Compare also Reinke, Wachsthumsgeschichte und Morphologic der Phanerogamenwurzek in 

 Hanstein's Bolanische Abhandlungen, Bonn 1871, Heft III. 



