MINUTE STKUCTTJRE OF LEAVES. 



Ill 



How does the epidermis of the two leaves compare ? 



Which has the larger stomata ? 



Which would better withstand great heat and long drought ? 



138. Chlorophyll as found in the Leaf. — Slice off a little 

 of the epidermis from some such soft, pulpy leaf as that of 

 the common field sorrel,^ live-forever, or spinach ; scrape from 

 the exposed portion a very 

 little of the green pulp ; 

 examine with the highest 

 power attainable with 

 your microscope, and 

 sketch several cells. 



Notice that the green 

 coloring matter is not uni- 

 formly distributed, but 

 that it is collected into lit- 

 tle particles called chloro- 

 phyll bodies (Figs. 96, 98) 

 and 205, e. 



139. Woody Tissue in 

 Leaves. — The veins of 

 leaves consist of fibro-vas- 

 cular bundles containing 

 wood and vessels much 

 like those of the stem of 

 the plant. Indeed, these 

 bundles in the leaf are 

 continuous with those of 

 the stem, and consist merely of portions of the latter, looking as 

 if unraveled, which pass outward and upward from the stem 

 into the leaf under the name of leaf-traces. These traverse the 

 petiole often in a somewhat irregular fashion. It is now easy 

 to see that the dots noted on the leaf-scars of the horse- 



ap. ap 



Fig. 98. — A Stoma of Thyme. 

 J, Surface vie^v ; 2, .Seotion ; e, epidermal 

 cells; s, guard-cells; x, stoma; ah, air- 

 chamher ; ap, pulp-cells of the leaf with 

 chlorophyll bodies, c; i, intercellular air- 

 spaces. (Both greatly magnified.) 



1 Bumex acetosella. 



