. Plants and their ways in South Africa. Botany; Botany. Stem and Root Structures 79 roots extending in four rows nearly its entire length. At the base of each root a slender horizontal slit is seen. A cut across the carrot shows a circle of tissue about midway between centre and circumference ; this region is actively divid- ing and adding to the thick- ness of the root. A carrot which has been left for a time in methyl blue will show traces of blue in the. Fig. 76. — Root of carrot, cross section. L, Cork ; tp, secondary parenchyma ; sx, secondary xylem. part enclosed within this circle whic
. Plants and their ways in South Africa. Botany; Botany. Stem and Root Structures 79 roots extending in four rows nearly its entire length. At the base of each root a slender horizontal slit is seen. A cut across the carrot shows a circle of tissue about midway between centre and circumference ; this region is actively divid- ing and adding to the thick- ness of the root. A carrot which has been left for a time in methyl blue will show traces of blue in the. Fig. 76. — Root of carrot, cross section. L, Cork ; tp, secondary parenchyma ; sx, secondary xylem. part enclosed within this circle which indicates, as in the stem, the region of wood vessels. They are surrounded by an abund- ance of storage tissue of which the carrot largely consists. Although the carrot has been immersed, a layer of cork pre- vents the surface of the carrot from absorbing the solution. If a cross section is stained with iodine, the medullary rays may be traced by the starch they contain. This is most abun- dant outside of the active ring where the rays extend through the phloem. Either a cross section or one cut lengthwise shows the lateral roots extending to the central portion of the root. Un- like leaves and branches, they arise in deep seated tissue and make their way through the cortex of the main root. While points of resemblance may be seen between a stem and a root, they show in their general form essential points of difference. 1. A root is protected by a root cap which is constantly worn away as it pushes its way through the soil. A stem is protected by the young leaves which form the bud. 2. Roots give rise to roots, stems [)roduce stems and also, unlike members, leaves. 3. Lateral roots arise within deep-seated tissue (endogen- ously) ; lateral branches and leaves arise from surface tissues (exogeiiously). 4. The stele in roots is relatively small, that is, the rigid. Please note that these images are extracted from scanned page images that may have been digitally enhanced for r
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1915
