8PERMAPHYTES. 81 



Xylem, consisting of : 



7. Large vessels or tracheae. 



8. Tracheids, smaller in cross-section than the 



vessels. 



9. Wood parenchyma (?). Thin-walled cells with 



cell-contents. 

 Phloem, consisting of : 



10. Sieve-tubes, thin-walled and in some places 



showing the perforated ends of the cells. 



11. Bast-cells, thick-walled. 



Sketch accurately a feiv cells of each kind in their 



relation to one another. 

 B. Monocotyledon. 



Observe with the naked eye the cut end of a stem 

 of Indian corn. Note : 



1. The firm outer layer (epidermis and sub- 



epidermis). 



2. The fundamental parenchyma. 



3. The isolated fibrovascular bundles. 



Make thin cross-sections through the outer part of 

 the stem. Mount in dilute glycerine and study 

 ivith A A 2 and D 2. 

 Observe in the bundles : 



4. The two large pitted tracheids. 



5. The smaller, spiral and annular vessels (one 



or more) between the tracheids and nearer 

 the centre of the stem. In many instances 

 the cells immediately surrounding these 



