198 PRACTICAL BOTANY. 



The structure and mode of origin of the young- 

 leaves should also be observed in the median longi- 

 tudinal sections. 



The Eoot. 



XIV. Cut transverse sections of the root of the Male 

 Fern, selecting for that purpose the thickest part of 

 an old root : mount in glycerine, and observe 



1. There is not any well-marked epidermis : single 

 superficial cells have grown out as root-hairs, remnants 

 of which may still be seen. 



2. The greater part of the section consists of the 

 bulky, brown-walled Cortex, of which the outer parts 

 are thin-walled ; but, passing inwards, there is a sudden 

 increase in thickness of the walls, so as to form a dense 

 sclerenchymatous ring : this surrounds 



3. The Bundle-sheath, which consists of a single 

 layer of cells flattened tangentially, and having the 

 usual dotted marking of the radial walls. [N.B. This 

 may be difficult to observe as the radial walls are often 

 pressed out of shape.] Within this layer lies 



4. The Phloem-sheath, which usually consists of 

 two layers of cells, with thin walls, and obvious proto- 

 plasmic contents. The vascular tissues inclosed within 

 these layers are arranged according to the ordinary 

 radial type ; thus there will be seen 



5. Two groups of Xylem abutting on the phloem- 

 sheath, and composed of Tracheides of various size, 

 the largest being near the centre of the root: the 

 two originally separate groups of xylem unite at the 

 centre by formation of fresh tracheides, and together 



