. Nature and development of plants. Botany. 402 THE PANDALES thickly populate an extensive marsh. The aerial stems live but for a year and are rather weak, but owing to the sheathing bases of the leaves they become sufficiently rigid to support a heavy foliage and withstand the winds. Notice also the extreme light- ness of these organs. This is due to the larger air spaces which also permit a ready interchange of gases from the leaves to all parts of the plant, even throughout the submerged rhizomes. You would naturally expect to find this structure in all aquatics since the roots at least are
. Nature and development of plants. Botany. 402 THE PANDALES thickly populate an extensive marsh. The aerial stems live but for a year and are rather weak, but owing to the sheathing bases of the leaves they become sufficiently rigid to support a heavy foliage and withstand the winds. Notice also the extreme light- ness of these organs. This is due to the larger air spaces which also permit a ready interchange of gases from the leaves to all parts of the plant, even throughout the submerged rhizomes. You would naturally expect to find this structure in all aquatics since the roots at least are submerged and all living cells require an interchange of gases (see page 54). The leaves are long. Fig. 279. Sectional view of seed of Veltheimia. of a large cotyledon, c, and laterally placed stem, i, e, endosperm; mi, micropyle; /, funiculus. The embryo consisting below which is the root, and narrow and point nearly straight up in the air. This pre- vents shading and permits the association of the plants in dense colonies. The leaves are covered with a waxy coating or bloom to prevent the adhesion of water and the plugging of the stomata. This device is often to be seen on the leaves of plants that are subject to heavy dews or rains. Moisture is frequently not evaporated from the leaves until near midday, and if the stomata become filled with water, there can be no interchange of gases for photosynthesis during this time. The flowers are of a very primitive type, consisting of naked. 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 Curtis, Carlton Clarence, 1864-1945. New York, H. Holt
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