. Botany, with agricultural applications. Botany. 200 STEMS by the cork formed beneath and gradually thickened as the stem grows older. In some cases the cork cambium produces cortex cells on its inner side as well as cork on its outer side, in which case the cortex is increased in thickness. Since cork is imper- vious to water, the tissues on its outside, having their water supply cut off, soon die and with the epidermis and cork form the dead outer bark. In a few trees like the Beech and Fir the original cork cambium may renew its activity year after year, but usually the cork cambium is rep
. Botany, with agricultural applications. Botany. 200 STEMS by the cork formed beneath and gradually thickened as the stem grows older. In some cases the cork cambium produces cortex cells on its inner side as well as cork on its outer side, in which case the cortex is increased in thickness. Since cork is imper- vious to water, the tissues on its outside, having their water supply cut off, soon die and with the epidermis and cork form the dead outer bark. In a few trees like the Beech and Fir the original cork cambium may renew its activity year after year, but usually the cork cambium is replaced each year by a new one formed just beneath. The inner bark consists of the inner cortex and the elements of the phloem made up of sieve tubes, com-. FiG. 179. — Cross section through the stem of a Red Oak, showing heartwood and sapwood. panion cells, parenchyma cells, and bast fibres. After years of growth the outer layers of phloem die and thus on trunks of trees of much age, the inner living bark contains only the inner layers of phloem, the older layers of phloem having become a part of the outer bark. Due to the addition of cork and the increase of the phloem and woody cylinder in thickness, the bark, which is un- able to increase in circumference except in a few cases, as in Beeches, is usually broken and slowly exfoliated. It is usually broken into fiurows, which are thought to serve the same purpose as lenticels in letting air into the stem tissues beneath. The woody cylinder, consisting of the xylems of numerous vas- cular bundles closely joined, functions chiefly in the conduction. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Martin, John N. (John Nathan), b. 1875. New York, John Wiley & sons, inc. ; [etc. ,etc. ]
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectbotany, bookyear1920
