PRIMARY MERISTEM. 87 



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

 are cut ofE 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 



Fig. 76.— Longitudinal section of apex of stem of a moss {Fontinaiis anUpyretica). 

 V, apical cell, forming eegmenta (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 ; », apical cell *of lateral leaf-forming shoot, arising 

 helow a leaf ; c, first cell of leaf ; b, cells forming cortex.- After Leitgeb. 



occupies approximately the same position in the organs of 

 Phanerogams as the apical cell 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. 



