130 



PHYSIOLOGICAL BOTANY. 



395. Thus the cell appears to be the type of every form of 

 tissue, the material of which the vegetable fabric is built, and 

 the laboratory where the work is performed. 



Name 



389. 



do we find pitted cells ? Show them. Explain fig. 474. 391. What is Trachenchyma f 



How are these tubes made ? Show the structure of dotted ducts (480). 393. Office of 



Cienchyma ? 394. Nature of these tubes ? What of intercellular passages ? 395. Give, 



finally, the import of the cell. 



CHAPTER III. 



THE EPIDERMAL SYSTEM 



Includes the external covering of all herbaceous growths 

 viz., the epidermis, stomata, hairs, glands, cuticle, etc., organs 

 which in older stems give place to bark. 



495 



494 



19t, Cells of epidermis with a stoma from leaf of Ilelleborus fcetidns. 495, Vertical section of a stoma of 

 Narcissus a, cuticle. 496, Epidermis cells with gtomata of Tradescantia Virginica. 



396. The epidermis (skin) consists of a layer of united, empty 

 cells, mostly tabular, forming a superficial membrane. It in- 

 vests all plants higher than Mosses, and all parts save the ex- 

 tremities, the stigma, and rootlets. Its office is to check evapo- 

 ration. That delicate membrane which may be easily stripped 

 off from the leaf of the Houseleek or the garden Iris is the epi- 



