THE GROUPS OF TISSUES. OR TISSUE-SYSTEMS. 37 



ular to its axis, but more frequently they are oblique to it. 

 In most mosses, for example (Fig. 35), the apical cell is a 

 triangular, convex-based pyramid, whose apex is its proxi- 

 mal portion. The successive segments are cut ofE from the 

 apical cell by alternate partitions parallel to its sides, thus 

 giving rise to three longitudinal rows of cells. Most ferns 

 and their relatives have an apical cell not much different 



Fig. 25. — Longitudinal section of apex of stem of a Moss (Fontinalis an- 

 tii)yreriea) . v, apical cell ; z, apical cell of lateral leaf -forming shoot, 

 arising below a leaf ; c, first cell of leaf ; 6, Z), 6, cells forming cortex. 



from that of the majority of mosses. In Horsetails, for 

 example, it is an inverted triangular pyramid having a 

 convex base. The segments (daughter-cells) are cut off by 

 alternating partitions parallel to the plane sides of the 

 pyramid, as in the mosses. In some mosses and ferns, how- 

 ever, the apical cell is wedge-shaped — i.e., with only two 

 surfaces — and in such cases two instead of three rows of 

 meristem-cells are formed. 



58. In the flowering plants the primary meristem is 

 usually developed from a group of cells, instead of from a 



