HISTOLOGY OF HIGHER PLANTS 



63 



of this plant are long and narrow, somewhat resembling those of 

 grasses. There is a pronounced midrib and the so-called veins 



J). 



FIG. 26. Histology of the Leaf of Tradescantia viryinica. 



A. Part of a transverse section of the leaf. 



B. Piece of the epidermis stripped from the lower surface of the leaf. 



(7. Chlorophyll cells from the mesophyll, as seen in a longitudinal section of the leaf. 



D. Portions of four vessels from a vascular bundle, with spiral and annular markings, as 

 seen in a longitudinal section of the bundle. 



(All more or less highly magnified.) 



a.c, air-cavity ; c.c. chlorophyll cell ; cp. chloroplastids ; ep.c. epidermic cell ; epd. epi- 

 dermis; g. c. guard-cell ; rues, mesophyll ; mi. nucleus ; par. colourless parenchyma ; 

 s/(.. sheath of vascular bundle, composed of thin-walled cells containing starch grains ; 

 sk. thick-walled skeletal tissue; st. stoma ; i.b. vascular bundle; ves. vessels. 



run parallel with one another from base to apex, as in all typical 

 Monocotyledons. 



If we cut a thin transverse section of a living leaf and 

 examine it under the microscope in a drop of water (Fig. 26, A) we 



