SELAGINELLA. SPOROPHORE. 171 



1. The arrangement of the cells at the summit of 

 the apical cone, which is terminated by an apical cell ; 

 from this segmental cells are successively cut off. 



2. The origin of the leaves is not from a single cell, 

 but by the outgrowth and subsequent division of a 

 number of cells at the periphery of the apical cone. 



In such median longitudinal sections should also be 

 observed the differentiation of the vascular bundle from 

 the primary meristem, and also the development of 

 the lacunar tissue, and its relation to the central 

 bundle. 



Preparations may also be made of the apex so as to show the 

 structure of the apical cone as seen from above. By comparison 

 of a number of these it may be seen that the form of the apical 

 cell is by no means constant, but varies between the forms of a 

 two-sided and a three-sided cone. 



X. Cut longitudinal sections through fertile branches 

 similar to those cut from the vegetative bud, and 

 examine them under a low power. 



Observe that the general arrangement of the stem, 

 leaves, and ligules is the same as in the vegetative bud. 

 In the lower part of the sections a mature Sporan- 

 gium may be found in the axil of each leaf. (The 

 sporangium may have lost its spores partially or 

 entirely during the preparation of the sections.) It 

 will consist of 



(a.) A short massive Stalk. 



(&.) A Wall enclosing the central cavity : the wall 

 will be found under a high power to consist of three 

 layers of cells 



i. The outer consisting of thick-walled cells, more 

 or less elongated radially. 



