. Botany; an elementary text for schools. Plants. 266 STRUCTURE OF STEMS AND ROOTS. 431. Usually very early iu the life of the stem a corhj 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 were located. The epidermis is first crowded off at these places, and the rough corky spots are called lenticels. Phellogen is very active in the cork oak of Spain, but we find it in nearly all woody plants. In such plants as button wood (syca- more), in which the bark peels off in thin
. Botany; an elementary text for schools. Plants. 266 STRUCTURE OF STEMS AND ROOTS. 431. Usually very early iu the life of the stem a corhj 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 were located. The epidermis is first crowded off at these places, and the rough corky spots are called lenticels. Phellogen is very active in the cork oak of Spain, but we find it in nearly all woody 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 study phellogen 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 basswood stem, j years old. The cone-shaped growths of phloem are plainly i. 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 Co.
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