PRIMARY MERI8TEM. 



87 



A, side view, B, a section). The segments (daughter-cells) 

 are cut off by alternating partitions parallel to the plane 

 sides of the pyramid, as in the mosses. In some of the 

 Bryophytes and Pteridophytes 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. 



111. In the Phanerogams the Primary Meristem is de- 

 veloped from a group of cells, instead of from a single one ; 

 they therefore have no apical cell. This group of cells 



n 



Fig. 76. Longitudinal section of apex of stem of a moss (Fontinalis antipyretica). 

 v, apical cell, forming segments (3 rows), each segment divided into an outer cell, 

 a, and an inner one the former develops cortex of the stem and a leaf, the latter 

 the inner tissue of the stem ; z, apical cell of lateral leaf-forming shoot, arising 

 below a leaf ; c, first cell of leaf ; 6, cells forming cortex. After Leitgeb. 



occupies approximately the\ same position in the organs of 

 Phanerogams as the apical ^ell does in the Bryophytes and 

 Pteridophytes ; it is composed of cells which have the power 

 of indefinite division and subdivision. 



112. The apical cell, and its actively growing daughter- 

 cells in its immediate vicinity, or in the case of the Phanero'- 

 gams the apical group of cells, with their daughter-cells, 

 constitute the Growing Point or Vegetative Point (Punctum 

 vegetationis) of the organ. When this active portion is 

 conical in shape it is the Vegetative Cone of some authors. 



