. Botany, an elementary text for schools. Botany. 26() STRUCTUEE OF STEMS AND EOOTS. .431. Usually very early in the life of the stem a corlnj layer of bark is produced. This is the product of an active layer of cells called phellogen. This layer is first found at those places where the stomates or breathing pores M^ere located. The epidermis is first crowded off at these places, and the rough corkj- spots are called lenticels. Phellogen is very active in the cork oak of Spain, but we find it in nearlj^ all wood}' plants. In such plants as button wood (syca- more), in which the bark peels off
. Botany, an elementary text for schools. Botany. 26() STRUCTUEE OF STEMS AND EOOTS. .431. Usually very early in the life of the stem a corlnj layer of bark is produced. This is the product of an active layer of cells called phellogen. This layer is first found at those places where the stomates or breathing pores M^ere located. The epidermis is first crowded off at these places, and the rough corkj- spots are called lenticels. Phellogen is very active in the cork oak of Spain, but we find it in nearlj^ all wood}' plants. In such plants as button wood (syca- more), in which the bark peels off in thin, flat layers, the phellogen layer is nearly uniformly active in all parts, while in many other cases there is very little unifor- mity. In wahoo (burning bush) it is in four bands, giving rise to four corner wings. In the section of menispermum already studied, it is found only under the lenticel spots where the stomates have been located. Fig. 409 shows structure of the outer bark as found in the whole circum- ference of the three-year-old stem of red currant. To studij phellogeti and corky tissue : Cut thin cross- sections of red currant from stems two or three years old which have been kept in alcohol at least several hours. The sections should be stained. With the highest power make a careful study of 408. Section of b!is>\\ood stem, 5 years oUl. The coue-shaped growths of phloem are plaiuly 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 Bailey, L. H. (Liberty Hyde), 1858-1954. New York Macmillan
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