. A text-book of botany for secondary schools. Botany. 30 A TEXT-BOOK OP BOTANY .r such a plant grows in the shade the leaves do not assume the profile position. It must not be supposed that there . is any accuracy in the north or south direction, as the edgewise position is the significant one. In the rosinweed probably the north and south di- rection is the prevailing one; but in the prickly lettuce, a very common weed of waste grounds, and one of the most striking of the compass plants, the edgewise position is frequently as- sumed without any ref- erence to the north or south direction of
. A text-book of botany for secondary schools. Botany. 30 A TEXT-BOOK OP BOTANY .r such a plant grows in the shade the leaves do not assume the profile position. It must not be supposed that there . is any accuracy in the north or south direction, as the edgewise position is the significant one. In the rosinweed probably the north and south di- rection is the prevailing one; but in the prickly lettuce, a very common weed of waste grounds, and one of the most striking of the compass plants, the edgewise position is frequently as- sumed without any ref- erence to the north or south direction of the apex (Fig. 26). (9) Motile leaves have the power of shifting their positions according to their needs, directing their flat surfaces toward the light, or more or less inclining them. Such leaves have been developed most extensively in the great family to which peas and beans belong, the most conspicuous ones being those of the so-called sensitive plants. The name has been given because the leaves respond to various external influences by changing position with remarkable rapidity. A slight touch, or even jarring, will call forth a response from the leaves; and the sudden ap- plication of heat gi\'es striking results (Fig. 27). The most common sensitive plant abounds in dry regions, and may be taken as a type of such plants. The leaves are divided. Fig. 26.—Prickly leHuce. showing tlie edge- wise or profile leaves from two points of 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 Coulter, John Merle, 1851-1928. New York, D. Appleton
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1906
