. Elementary botany . Botany. METAMORPHOSED SHOOTS 37 render it a matter of difficulty to recognise them as such. For instance, stems may assume the appearance of leaves; stems, leaves, or parts of them, may appear in the form of spmes or of tendrils. It is mainly by the study of their arrangement that we can recognise as such these meta- morphosed stems and leaves, and can distinguish them from " subsidiary ; SPINES, THORNS, AND PRICKLES. Many plants are armed with sharp-pointed woody structures, which may represent stems, leaves, or subsidiary outgrowths. (i.) Stem-spine
. Elementary botany . Botany. METAMORPHOSED SHOOTS 37 render it a matter of difficulty to recognise them as such. For instance, stems may assume the appearance of leaves; stems, leaves, or parts of them, may appear in the form of spmes or of tendrils. It is mainly by the study of their arrangement that we can recognise as such these meta- morphosed stems and leaves, and can distinguish them from " subsidiary ; SPINES, THORNS, AND PRICKLES. Many plants are armed with sharp-pointed woody structures, which may represent stems, leaves, or subsidiary outgrowths. (i.) Stem-spines.—The spines of the Hawthorn (fig. 58) occupy the po- sition of branches, for they stand in the axils of leaves ; they bear small leaves, whicli soon fall off. These spines, there- fore, represent stems of definite growth, whose growing points become hard and woody. Certain branches of the Pear-tree often end in spines, which, therefore, are metamorphosed stems. (ii.) Leaf-spines.—The leaves of Thistles and of the Holly have spinose outgrowths, which are obviously portions of the lamina. The Barberry- plant has branched spines, in whose axils branches arise: hence they are metamorphosed leaves. This view is confirmed by the fact that on a stem of the Barberry it is often possible to see all the transition stages between the gr'een leaves and the branched spines. Each foliage-leaf of many Acacias has two spines occupying the position of the two stipules: therefore the spines are metamorphosed stipules. The Common Furze or Gorse {Ulex europaa) has thorns, some of which possess axillary buds, and others of which terminate stems. Thus in this plant both leaves and stems have changed to form Fig. 58.—Shoot of Hawthorn with a stem-spine (rf) in the axil of a leaf. « represents stipules; b denotes the lamina. (After Dennert.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and app
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectbotany, bookyear1898
