176 PRACTICAL BOTANY. 



sporangia, are erect and elongated ; their lower part 

 is covered sparsely with leaves of small size : about 

 1 2 inches below the apex they usually divide into 

 two or three branches, covered with rather broader, 

 closely imbricated leaves : from the upper surface of 

 each of these rises one Sporangium, which is yellow 

 when ripe, and opens by a split parallel to the plane of 

 the leaf which bears it. 



II. Cut transverse sections of a fully developed stem. 

 Mount some of them in glycerine, others in Schulze's 

 solution, and examine with a low power: externally 

 will be found 



1. An Epidermis, consisting of a single layer of 

 cells; their outer walls are thick, and covered by a 

 continuous layer of Cuticle, which may be recognised 

 in thin sections by its high refractive power. 



2. Below the epidermis lies a broad band of Cortical' 

 tissue, which appears differentiated into successive 

 thinner bands according to the thickness of the cell- 

 walls : thus there may be distinguished 



a. An external sclerenchymatous band, with thick 

 lignified walls (brown with Schulze's solution) ; small 

 intercellular spaces may be seen at the angles between 

 the cells : these cells retain a small proportion of their 

 cell-contents. 



b. Within this is a broad band of thin-walled 

 tissue, in which the cell-contents are not apparent : 

 the cell-walls are tinged with pink in Schulze's solu- 

 tion. There is a gradual transition from this to 



c. The most central part of the cortex, which 

 is strongly sclerenchymatous; it has intercellular 

 spaces, and retains its cell-contents. It forms a dense 



