. Foundations of botany. er-inch, for de-tails. With the lowpower, note: (rt) The brownlayer of outer bark. (b) The paler layerwithin this. (c) The woody cyl-inder which formsthe central portion ofthe root. The distinction be- tween (h) and (c) is more evident when the section has been exposed to the air for a few minutes and h, root-hairs with adhering hits of sand ; e, epidermis ; changed somewhat ins, thin-walled, nearly globular cells of bark ; b, hard ^^Jq^,^ j^. jg ^ ^^^^bast; c, cambium ; w, wood-cells ; d, ducts. * _ ° plan to look with the low power first at a thick section, viewed as
. Foundations of botany. er-inch, for de-tails. With the lowpower, note: (rt) The brownlayer of outer bark. (b) The paler layerwithin this. (c) The woody cyl-inder which formsthe central portion ofthe root. The distinction be- tween (h) and (c) is more evident when the section has been exposed to the air for a few minutes and h, root-hairs with adhering hits of sand ; e, epidermis ; changed somewhat ins, thin-walled, nearly globular cells of bark ; b, hard ^^Jq^,^ j^. jg ^ ^^^^bast; c, cambium ; w, wood-cells ; d, ducts. * _ ° plan to look with the low power first at a thick section, viewed as an opaque object, and then at a very thin one mounted in water or glycerine, and viewed as a transparent object. Observe the cut-off ends of the ducts, or vessels, which serve as passages for air and water to travel through ; these appear as holes in the section, and are much more abundant relatively in the young 1 Young suckers of cherry, apple, etc., which may be pulled up by theroots, will afford excellent Fig. 21. —Much Magnified Cross-Section of aVery Young Dicotyledonous Root. ROOTS 45 than in the older and larger portions of the root. Sketch one sectionof each kind. Examine with a higher power (100 to 200 diameters), and note theends of the thick-walled wood-cells. Compare these with Fig. 72. Notice the many thinner-walled cells composing stripes radiatingaway from the center of the root. These bands are the medullaryrays, whose mode of origin is shown in Fig. 68. Moisten some ofthe sections with iodine solution,^ and note where the blue colorshows the presence of starch. Split some portions of the root throughthe middle, cut thin sections from the split surface, and examine withthe high power some unstained and some stained with iodine. Notice the appearance of the wood-cells and the ducts as seen inthese sections, and compare with Fig. 58.^ 56. Structure and Contents of a Fleshy Root. — In somefleshy roots, such as the beet, the morphology of the parts
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectplants, bookyear1901
