110 PRACTICAL BOTANY. 



II. Cut longitudinal sections of the same, treat as 

 before, and observe 



a. The Epidermis composed of oblong cells. 



&. The prosenchymatous cells of the Sclerenchyma. 



c. The ground parenchyma with roundish cells. 



d. The Vascular bundles pursuing a longitudinal 

 course parallel to one another, without lateral fusion. 



In the Xylem observe 



i. The annular, spiral, and pitted vessels, and 

 note, especially in the latter, the clearly-marked joints, 

 pointing to their origin from a succession of cells. 



ii. The pitted Tracheides. 



iii. The thin-walled Parenchyma. 



And in the Phloem (which is easily recognised 

 by its cellulose walls, blue with Schulze's solution) 

 distinguish 



iv. The Sieve-tubes, which have a wide cavity, 

 intercepted here and there by transverse sieves. 



!N .B. If it be found difficult to distinguish the sieve- 

 plates, a fresh section may be treated with potash ; the 

 character of the sieve-plate is then more easily seen. 



v. The Cambiform cells, which are narrow and 

 pa renchymatous. 



Note the prosenchymatous constituents of the sheath 

 of Sclerenchyma, and observe transitional forms 

 between these and the pitted Tracheides (ii.) with 

 square ends, which belong to the xylem. 



III. Cut successive, thick transverse sections through 

 a node : treat them with strong potash [or better, 

 soak them for twenty-four hours or more in dilute 

 potash] ; mount in glycerine, and examine with a low 

 power. 



