76 PRACTICAL BOTANY. 



V. Cut radial sections from a four-year-old stem of 

 Elm ; soak them for ten minutes or more in alcohol (to 

 remove the air bubbles), and mount in glycerine. Use 

 a low power. 



It will be found difficult to cut good sections so as to include 

 the whole radial surface ; it is therefore better not to attempt it, 

 but to study the several structures in a number of successive 

 sections, each extending over only a part of the radial surface. 



Starting from the outside, observe the same succes- 

 sion of tissues as already seen in the transverse sections, 

 viz. : 



1. Epidermis, which is often dried up and dis- 

 organised. 



2. Cork (including the cork-cambium and peri- 

 derm), with the short cells arranged in radial rows. 



3. Cortical tissue, with large mucilage cells. 



4. Hard bast, consisting of long fibres. 



5. Soft bast, thin- walled elements with much 

 protoplasm. 



6. Cambium, a misty band ; cells not easily defined. 



7. Xylem, with thick lignified walls, the vessels 

 appearing as large tubular cavities. 



8. Pith, parenchymatous ; its appearance as in 

 transverse sections. 



Note the medullary rays, which appear as narrow 

 bands of parenchyma, following the plane of section. 



Examine these several tissues in detail with a high 

 power. 



1. The Epidermis, when still persistent, shows the 

 same characters as are observed in transverse sections. 



