CHAPTER XIV. 



Selaginella. 



In the species of Selaginella whose leaves have the 2^ 

 arrangement and stand in pairs opposite to one another in 

 four longitudinal rows, the form of the growing end of the 

 stem is that of a cone much flattened laterally. It projects 

 far beyond the place of origin of the youngest pairs of leaves 

 (PL LIV, figs. 3, 5, 7"). The multiplication of the cells of 

 the end of the stem goes on in the young shoot of S. hortensis, 

 Metten. [denticulata hortul.) until the commencement of 

 the formation of the third pair of leaves, and in S. Galeoltii 

 until that of the sixth pair. The multiplication is first pro- 

 duced by continual division of a single cell occupying the 

 apex of the blunt cone, by means of septa inclined alter- 

 nately to the right and to the left, always towards one of 

 the small sides of the terminal bud. The form of this cell 

 is that of a segment of an ellipsoid (PI. LIV, fig. 8 ; PI. LVI, 

 figs. 1, 3). The formation of the above septa, like all the 

 divisions of the cells of the end of the stem, is preceded by 

 the disappearance of the primary nucleus of the cell,* the 

 formation of two new smaller nuclei, and the appearance of 

 a dark line between the two newly-formed nuclei (PI. LIV, 

 fig. 9). This line is easily obliterated, even by the continued 

 action of pure water; its direction indicates that of the 

 future septum. It is the side-view of the surface of contact 

 of the two halves of the contents of the mother-cell. 



Contemporaneously with the commencement of a new 



* This primary nucleus is a globular vesicle floating freely in the fluid con- 

 tents of the cell which are rendered turbid by numerous granules. 



