. Botany for agricultural students . Botany. REPRODUCTIVE TISSUES 133 stored chiefly in the medullary rays during the previous season. For water storage some plants have special tissues, while others like the Cacti store it throughout the plant body. Secretory Tissues. — Secretory tissues, although not so essential and no so common among plants as the other tissues discussed, perform an important function in some cases. Most showy flowers have secreting tissues, known as neda glands, located at the base of the corolla or calyx. {Fig. 181.) These glands secrete the nectar, which, by attracting
. Botany for agricultural students . Botany. REPRODUCTIVE TISSUES 133 stored chiefly in the medullary rays during the previous season. For water storage some plants have special tissues, while others like the Cacti store it throughout the plant body. Secretory Tissues. — Secretory tissues, although not so essential and no so common among plants as the other tissues discussed, perform an important function in some cases. Most showy flowers have secreting tissues, known as neda glands, located at the base of the corolla or calyx. {Fig. 181.) These glands secrete the nectar, which, by attracting insects, aids in securing cross- pollination. Furthermore, honey is made from nectar, and the value of a plant as a bee-plant depends upon the amount and qual- ity of nectar secreted by its nectar glands. On the leaves, stems, or fruits of many plants, such as Mints, Oranges, Lemons, etc., there are glands whose secre- tions give the plan': a peculiar fragrance. In he stems and leaves of Conifers occur long tubes or ducts, known as resin ducts, which are lined with secre- tory cells that secrete resin from which pine tar, rosin, turpen- tine, and other valuable prod- ucts are made. Much Uke the Fig. 121.—A Buckwheat flower resin ducts are the milk or lac- with sepals removed from one side tif^ous vessels of the Milkweeds J^ ^^^^^^ ^^"^ar glands {n). After (Asclepiadaceae), Spurges (Eu- phorbiaceae), Dogbanes Apocynaceae), and other plant famihes where milk-like secretions occur. There are numerous secretions many of which, however, are secreted by cells in which secreting is not the special function. Reproductive Tissues. — Reproductive structures are of two kinds, sexual and asexual. Any portion of a plant, as a bud, tuber, stem, or root which may function in producing new plants, is regarded as an asexual reproductive structure. Some plants, as Irish Potatoes, Sweet Potatoes, and Strawberries illustrate, are quite generally propagated asexuaUy. In the higher plants
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
