CHAPTER VI. 

 THE EPIDERMIS STOMATA WATER-STOMATA. 



PRINCIPAL MATERIALS USED. 



Leaves of Flag Iris ; fresh. Or, of Hyacinth. 

 Leaves of Tradescantia virginica, or T. zcbrina ; fresh. 

 Leaves of L ilium ; in alcohol. 



Leaves of Aloe or Agave; fresh; or alcohol material softened for twenty- 

 four hours in half-and-half glycerine and alcohol. 

 Leaves of Tropwolum, or of Fuchsia ; fresh. 



PRINCIPAL EEAGENTS USED. 

 Chlorzinc iodine Sulphuric acid Tincture of alkanet Potash. 



Epidermis of Iris. Take a surface-section of the outer side 

 (morphologically the under side) of the "equitant" leaves of a 

 Flag Iris, Iris florentina. The section must be so thin that it 

 only grazes the tissue underlying the epidermis, and should be 

 observed in water with the outer surface turned upwards. It will 

 be seen at once that the Epidermis is composed of elongated cells 

 which run parallel to the long axis of the leaf. The cells are 

 ended by cross partition walls ; they are connected together 

 without any ordinary intercellular spaces, contain colourless cell- 

 sap, a nucleus, and a very reduced protoplasmic sac. On its 

 outer side the epidermis is covered by an exceedingly fine-grained 

 layer of wax. In a line with the cells of the epidermis lie 

 special intercellular spaces, the elliptic Stomata, which, however, 

 are only indistinctly visible, because the four adjoining cells of 

 the epidermis extend over the Guard-cells of the stoma, 1 partially 



1 In ordinary terminology, the term " stoma " includes the guard-cells 

 and the accessory structures. I have limited the term, as etymologically it 

 should be limited, to the pore (" stomatic cleft," of many authors). The 

 whole structure is a " stomatic apparatus". [ED.] 



(80) 



