VIL] THE BRACKEN FERN. 65 



ing some of the cells quite opaque and almost 

 black-looking. 



5. Cut a thin longitudinal section of the stem and 

 examine with i inch and then with ~ obj. Make 

 out the various tissues described in 3 and 4. 



a. The epidermis, subepidermis and parenchyma, 

 much as in the transverse section, except that 

 the subepidermic cells are longer. 



b. The sclerenchyma is seen to be made up of greatly 

 elongated cells, tapering towards each end. 



c. The vascular bundles; note in them 



a. The cells of the bundle sheath much as in the 

 transverse section; the bast fibres, elongated, 

 with thickened walls; the cells of the bast 

 parenchyma somewhat elongated ; the bast 

 vessels, elongated cells, presenting irregular 

 patches of pores (sieve-tubes) ; the bast sheath 

 cells somewhat elongated. 



ft. The vessels: elongated tubes presenting cross 

 partitions, dividing them into separate cells, 

 at long intervals. Two forms of vessel will 

 be seen, viz. scalariform vessels, with regular 

 transverse thickenings on their walls and 

 spiral vessels, less numerous than the last 

 form : with a continuous spiral thickening on 

 their walls. 



y. The bast cells: seven or eight times as long as 

 they are broad, and terminating obliquely at 

 each end. 



8. The elongated larger cells (4. d. 8) : they have 

 very slightly thickened walls and no scalari- 

 form markings. 

 M. 5 



