D. MERISTEM TISSUE. 



MERISTEM, or GENERATING TISSUE, is usually classified under two 

 heads, viz: 



I. Primary Meristem, giving rise to the PRIMARY STRUCTURE 

 in plants, such as young cellular tissue, and found at the apices 

 of young thallomes, stems and roots, and at the apex and base of 

 young leaves. 



II. Secondary Meristem, or CAMBIUM, giving rise to the 

 SECONDARY STRUCTURE, as the thickening growth of stems, roots of 

 DICOTYLEDONS, or EXOGENS. 



The SECONDARY MERISTEM, as PROCAMBIUM, forms a part of every 

 fibro-vascular bundle in its earliest stage. 



The Primary fleristem. 



TYPE A. Of a SINGLE APICAL OR INITIAL CELL. Found in most 

 of the higher CRYPTOGAMIA. 



TYPE B. Of a GROUP OF INITIAL CELLS. This is characteristic 

 of PHANEROGAMS. 



Illustration, Type B: Root from a cultivated Hyacinth grown 

 in a jar of water. 



PREPARATION FIRST: Trans - and longitudinal sections prepared 

 after the method on p. 21, also for serial sections, p. 35. (Fig. 16.) 



In the longitudinal section, observe the general arrangement 

 of the different layers of cells, viz: 



1. That the several series of cells converge into a rounded 

 cone at a point just back of the apex. This point is the center of 

 the so-called "Initial Group''' which constitutes the Primary Meris- 

 tem. It is impossible to say just how far meristematic cells extend 

 from this point. 



