such as onion, tulip, and lily and some of these contain valuable foods and drugs. The great majority of them are insect fertilized and are therefore wonderfully colored, and some furnish rich stores of honey. But the most highly developed and interesting of all the monocotyledonous plants are the orchids (Figures 89-92). This family, _Orchidaceæ_, [Illustration: FIG. 89.--ROSE POGONIA (_Pogonia ophioglossoides_) FIG. 90.--YELLOW-FRINGED ORCHID (_Blephariglottis ciliaris_) Fig. 89. Rose pogonia. A native bog orchid with purplish-pink flowers. Fig. 90. Yellow-fringed orchid. A bog and meadow orchid of the eastern United States.] comprises over 6,000 species and many varieties, the overwhelming proportion of which live in the tropics. Perhaps 90 per cent of them are epiphytes, or air plants, which are perched high up on the branches or bark of trees, and take all their food and water from the air. All the native orchids of temperate North America grow in the ground, however, and their food habits are unique. They depend for food upon a microscopic organism found inside the roots of all orchids, and which helps them to take in the food from the soil. So many of these orchids are partial saprophytes, and without the associated organism they could not grow. Almost uniformly the [Illustration: FIG. 91.--WHORLED POGONIA (_Isotria verticillata_) FIG. 92.--ARETHUSA (_Arethusa bulbosa_) Fig. 91. Whorled pogonia. A woodland orchid with the leaves and flowers whorled at the apex of the stem. Fig. 92. Arethusa. The most beautiful of our bog orchids, with a fringed lip and pinkish-purple flowers which bloom about Decoration Day. Note the highly irregular flowers in this and Figs. 89-91.]