THE LEAF 



167 



removed from the plant during the day time and viewed 

 under a high power, the chlorophyll bodies, on treatment 



P- 



Fbv 



ach 



Fbv 



FIG. 223. Transverse section through a leaf of beet: e, upper epidermis; e', 

 lower epidermis ; st, stoma ; a, air space ; p, palisade cells ; t, collecting cells ; sch, 

 spongy parenchyma ; i, i, intercellular air spaces ; Fbv, section of a vein (fibrovascu- 

 lar bundle). 



with iodine, will be seen to contain granules of starch which 



they are in the act of elaborating. The collecting cells, t, 



receive the assimilated product from the 



palisade cells and pass it on through the 



spongy parenchyma, sch, to the fibrovascular 



bundles. Notice how much more abundant 



the green matter is in the upper part of the 



leaf than in the lower ; has this anything to 



do with the deeper color of the upper surfaces 



, . x /\. ,, . . ,, FIG. 224. Chlo- 



of leaves? Notice the opening, st, in the rophyii bodies con- 

 lower epidermis ; do you recognize it? (See ^^ course oTTor- 

 Fig. 222.) It is a stoma, seen in vertical mation. Magnified 

 section. Notice the intercellular air spaces, ^ 

 i, i, in the spongy parenchyma, and the much larger one, a, 

 just behind the stoma. Why is this last so much larger? 



