162 PRACTICAL BOTANY 



which will be better understood on comparison of their 

 appearance in longitudinal sections. 



/>. 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. 



VII. As a preliminary to the study of longitudinal sections, 

 separate some pieces of the vascular bundles of Pteris or 

 Nephrodium 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 bundle 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 ele- 

 ments. 



Cut longitudinal sections of the stem of the Male Fern : first 

 take radial sections of the peripheral tissues, and treat as 

 above : note 



1. The epidermis with scaly out-growths. 



2. The subjacent ground tissue, and especially the scleren- 

 chyma consisting of cells of short prosenchymatous form, 

 with brown pitted walls, and cell-contents : note the gradual 

 transtion from sclerenchyma to 



3. The colourless ground tissue, with short parenchymatous 

 cells, and large intercellular spaces. 



VIII. Cut longitudinal sections so as to pass tangentially 

 through the central network of bundles : treat some sections 

 with chlor-zinc-iodine, and mount others in glycerine. Note 

 the several tissues observed in the transverse sections, and they 

 will show here the same position relatively to one another. By 

 reason of the frequent splittings and fusions of this bundle- 

 system the several elements will appear contorted and twisted, 

 but this does not materially affect their general arrangement, 

 which will be seen under a high power as follows : 



