290 PRACTICAL BOTANY 



peculiar structure which will be better under- 

 stood on comparison of their appearance in 

 longitudinal sections. 



b. Conjunctive parenchyma with cellulose 



walls, and protoplasmic contents with starch : 



these cells are distributed evenly throughout 



the xylem, and also form a band surrounding 



it completely. 



VIII. As a preliminary to the study of longitudinal 

 sections, separate some pieces of the vascular bundles 

 of Pteris or Aspid-ium from the surrounding tissue, and 

 warm them gently in a test-tube with a little potassium 

 chlorate and nitric acid, till the elements of the bumfle 

 may be separated easily one from another ; then stop 

 the action by diluting with water, and mount in water 

 or glycerine. By preparing them in this way the 

 tracheides, &c., may be subjected to separate examina- 

 tion, and their form and structure may be more exactly 

 made out. 



Apply the same process to the sclerenchyma, and 

 observe the form and marking of the walls of its 

 constituent elements. 



Cut longitudinal sections of the stem of the Male 

 Fern : first take radial sections of the peripheral tis- 

 sues, and treat as above : note 



1. The epidermis with scaly out-growths. 



2. The subjacent ground tissue, and especially the 

 sclerenchyma consisting of cells of short prosenchy- 

 matous form, with brown pitted walls, and cell-contents : 

 note the gradual transition from sclerenchyma to 



3. The colourless ground tissue, with short 

 parenchymatous cells, and large intercellular spaces. 



