346 HOFMEISTER, ON 



fig. 23). The protuberance has the form of an ellipsoid flat- 

 tened on the upper and under side, and is separated from 

 the original cavity of the mother-cell by a septum (PL 

 XLVI, fig. 24). The roundish cell, not unlike a knobby 

 hair, which is now seated at the base of the fore side of the 

 leaf, is the primary cell of the single scale which it produces. 

 Its first divisions exactly resemble those of the cell of the 

 first degree of one of the gemmae of Marchantia or Lunu- 

 laria. The cell is divided two or three times by transverse 

 septa, which are at right angles to the future longitudinal 

 axis of the scale, and perpendicular to its surfaces (PI. 

 XLVII, fig. 1). The apical cell then divides, and after it 

 the lower cells also, by a longitudinal septum at right angles 

 to the one previously formed. The halves increase — after 

 new transverse septa have been formed in each of the two 

 upper cells — by the growth of septa parallel to the free 

 outer edges of the scale, followed by septa produced in the 

 outer of the newly formed cells at right angles to the outer 

 margin. The organ which has now the shape of a blunt 



O O J- 



spatula (PI. XLIX, fig. 4), continues to increase the number 

 of its cells by the division of those of its circumference by 

 means of longitudinal and transverse septa which alternate 

 with tolerable regularity. This activity of the cells terminates 

 much sooner at the apex of the leaf than at its base, where 

 an intercalary multiplication of the cells occurs, mainly in 

 a longitudinal direction, some time after the cells of the apex 

 of the leaf have lost their power of division. The scale be- 

 comes pointed and heart-shaped (PI. XLIX, fig. 5). 



All these septa are perpendicular to the surfaces of the 

 scale. Soon, however, septa parallel to its surfaces appear 

 in its middle cells (PL XLVII, fig. 2). Thence the divi- 

 sion advances towards the cells of the base of the leaf, 

 which are engaged in intercalary multiplication in length 

 and breadth. In the cells nearest to the base the divi- 

 sion is sometimes repeated, so that this part of the scale 

 consists of three layers. The remainder of it has two 

 layers, with the exception of the margin and the top, 

 which always exhibit a single layer of cells. Individual 

 cells of the margin grow out into rather long pointed 

 papillae. 



