vi HOW TO PREPARE AND EXAMINE SECTIONS 65 



Cells. If a thin transverse section of the stem of the sun- 

 flower be made, and examined with a hand-lens, a number of 

 openings will be seen ; these represent the elementary parts 

 of the plant, and are called cells. The portion of the cell which 

 surrounds the soft material is called the cell- wall, and in our 

 section is the most prominent part of the cell. The soft 

 material receives the name of protoplasm, and is the most 

 important part of the cell. All plants are built up of cells, and 

 these are arranged to form definite structures, which receive the 

 name of tissues. 



EXPT. 53. Obtain a ripe Tomato and mount a small portion 

 of the inner pulp without water, and examine with a lens. Note the 

 cells are very large and oval, the cell-walls are very thin, and a thin 

 protoplasmic lining can be seen. 



EXPT. 54. Sow some seeds of the Sunflower in soil, and when 

 the stem is about six inches in length, cut transverse sections of 

 it. These should be placed in a watch-glass with a fifty % solution of 

 alcohol to clear them. Mount the thinnest section in glycerine and 

 examine with a lens. The cells are large and filled with protoplasm, 

 and are arranged in definite groups, 



EXPT. 55. From a small Beetroot cut a thin transverse section, 

 mount on a glass slip and examine with a hand-lens. Notice the 

 cells are filled with coloured cell-sap. Place the section in alcohol 

 for a few minutes and examine again ; the coloured cell-sap will have 

 oozed out. This is due to the spirits having killed the protoplasm. 



EXPT. 56. Cut a thin section from a Potato, mount and hold it 

 on the blade of the knife so that a portion is exposed to the light ; 

 examine with a hand- lens. Note the cells appear as minute bodies, 

 dark in colour, due to the air they contain. 



Tissues. If a transverse section of the stem of a Sun- 

 flower be made and examined (see Fig. 87), the cells are seen 

 to be arranged in a certain definite manner. On the outside 

 a single layer of cells is arranged to form a covering to the 

 stem. This covering forms the epidermis. In all cases the 

 cells which cover the plant, and protect the deeper parts from 

 injury, form the epidermal tissue. Within the section a 

 number of groups of cells can be seen forming a nearly complete 

 ring ; these are separated from the epidermis by a layer of cells. 

 This ring of cells forms the vascular tissue of the plant. The 

 separate groups of cells are called vascular bundles. In the 

 centre, and between the vascular ring and the epidermis, a 



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