100 PRACTICAL BOTANY. 



i.e. about two inches from the end. Treat with dilute 

 potash for about ten minutes, and mount in glycerine. 



N. B. It will be found convenient to hold the roots 

 in pith, or otherwise to imbed, while cutting the 

 sections. 



Observe the following tissues : 



1. At the centre of the circular section is a mass of 

 Parenchymatous Pith. At the periphery of this are 



2. Four radiating groups of elements of the Primary 

 Xylem, which are the most strongly marked tissues 

 of the young root. They have dark lignified walls 

 (test with Schulze's solution or aniline sulphate), and 

 resemble the primary xylem of the stem. Note fresh 

 elements in course of formation at their central limit. 

 The development is thus centripetal. Alternating with 

 these may be seen 



3. Four groups of Primary Phloem, which are not 

 as yet very well marked. These several groups of 

 elements are separated laterally from one another by 

 bands of parenchyma. At the periphery of the central 

 cylinder thus built up is 



4. The Pericambium or phloem-sheath, consisting 

 of thin-walled cells, arranged in an undulating band, 

 which is a single layer of cells in thickness, peripherally 

 to the phloem, but opposite the xylem it consists of two 

 to three layers of cells. 



5. Immediately outside this is the Bundle-sheath, 

 consisting of a single layer of cells, having the character- 

 istic dark dot on their radial walls. Then follows 



6. The parenchymatous Cortex, a thick band of 

 tissue, with intercellular spaces, and 



7. The Epidermis, a single layer, not well marked. 



