vin THE HISTOLOGY OF THE TISSUES 97 



EXPT. 88. Obtain either the stem of the Pumpkin or of the 

 Cucumber ; harden in alcohol. Cut either radial or tangential longi- 

 tudinal sections. Stain in iodine solution, 

 and mount a few in glycerine. Note 



(i) The sieve tubes, the transverse walls of 

 which are clearly seen owing to the substance 

 which surrounds them being stained dark 

 brown, the wall only staining faintly yellow. 



The substance which surrounds the sieve 

 plates is called callus, and it is probably com- 

 posed of cellulose. The amount of callus 

 present will depend upon the age of the sieve 

 tubes, and the season of the year. 



(ii) The protoplasm which lines the tubes 

 and is well developed just over the sieve- 

 plates. 



(iii) The shape of the sieve tubes. 



(iv) The companion cells. These are long 

 and narrow and their nuclei can be clearly 

 seen under the high power. 



EXPT. 89. From the lower side of the leaf 

 of the Wallflower pull off a small portion of 

 the epidermis ; this can be done by raising 

 the epidermis with a knife and gently pulling 

 at it ; as a rule the edge of the piece of 

 epidermis will be thin enough for examination. 

 Mount in water, and examine it with the high 

 power. Note 



(i) The sinuous outline of the cell-wall. 



(ii) The spindle-shaped hairs which lie close 

 to the surface of the leaf. 



(iii) The stomata, which are very numerous. 

 Each stoma is surrounded by a pair of sausage- 

 shaped cells the guard-cells. 



EXPT. 90. Strip from the underside of the FlG 127 ._Digestive 

 leaf of the Hyacinth (the leaf of any mono- gland of the Sun- 



cotyledonous plant will do as well) a small dew - (x6o.) (S.) 



portion of the epidermis. Mount in water and 

 examine first under a low power, then with the high power. Note 



(i) The epidermal cells. 



(ii) The stomata, which are very large and numerous. 



Strip from the upper surface of the leaf a piece of epidermis and treat 

 in the same way. 



(iii) Compare its appearance with the lower epidermis and note in 

 what ways they agree and how they differ. 



EXPT. 91. Mount in water the rootof a germinating Mustard Seed ; 

 examine it under a low power. Note 



(i) The root-hairs ; these are unicellular, and are formed by the out- 

 growth of the cells of the apidermis. 



H 



