100 M Kit 1ST KM T/SsrE. 



2. The Cctlyptrogen, a row of cells on the apical skle of the 

 luitial Group, producing rows of cuboidal cells radiating towards 

 the apex of the root, the outer ones becoming rounded and loosely 

 coherent. 



3. The DermatOffen, arising from the Initial Group curving 

 to the right and left and ultimately producing a double layer of 

 cuboidal or flattish cells bounding the section on each side. In 

 large roots it consists of more than two rows of cells. 



4. The Plerome, axial rows of oblong or cuboidal cells form- 

 ing a central band immediately back of the Initial Group. 



5. The Periblem thin-walled cells of various forms in several 

 rows between the Plerome and Dertnatogen. 



6. That the differentatiou into the above named layers occurs 

 at a very early period in the development of the root-tissues. They 

 retain their original distinctness after passing over into permanent 

 tissue when they are named as follows: 



The Calyptrogen gives rise to the Root-Cap. 



The Demiatogen gives rise to the H]>i<l< /////*. 



The Periblem gives rise to the Cortex or Cortical Parenchi/in<(. 



The Plerome gives rise to the Axial or Central Cylinder. 



1. The first appearance of Spiral Vessels on the right and 

 left margin of the Plerome. Trace them backwards. They repre- 

 sent the beginnings of the Fibro- Vascular Bundles which always 

 arise within the Plerome in both stem and root. 



8. The two rows of cells on the peripheral side of the Spiral 

 Vessels. The inner (the Pericambiuiti) belongs to the Plerome, 

 the outer (the Endodertnis) belongs to the Periblem or Cortex. 

 The Endodermis is sometimes called the -'Plerome-sheath" or 

 "Bundle-sheath/' 



9. The peripheral layers of cells of the Plerome itself, extend- 

 ing back from the Initial Group to the beginning of the Fibro- 

 Vascular Bundles. These are termed collectively the Procambium, 

 as it is from such cells that the tissues of the Bundles themselves 

 arise by fission and differentiation. 



10. Occasional dark lines along the lateral walls of the Cortex 

 cells. These are due to cylinders of air in narrow intercellular 

 spaces. (See 2 under observations below on the cross-section.) 



