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 nectar glands, located at 

 the base of the corolla or calyx. (Fig. 121.} 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 plant a peculiar 

 fragrance. In the 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 like the 

 resin ducts are the milk or lac- 

 tiferous vessels of the Milkweeds 

 (Asclepiadaceae) , Spurges (Eu- 

 phorbiaceae) , Dogbanes (Apocynaceae) , and other plant families 

 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 asexually. 



In the higher plants the sexual reproductive tissues are those 

 of the flower, and more especially those of the stamens and pistils 

 with which the student is familiar. Although the eggs and sperms 



FIG. 121. A Buckwheat flower 

 with sepals removed from one side 

 to show the nectar glands (n) . After 

 H. Miiller. 



