similar manner, there are differences which might not at first be suspected. Thus in some cases, as, for instance, the pine, it is the seed itself which is winged; in Thlaspi arvense it is the pod; in Entada, a leguminous plant, the pod breaks up into segments, each of which is
Fig. 12.—a, maple; b, sycamore; c, lime; d, hornbeam; e, elm; f, birch; g, pine; h, fir; i, ash.
winged; in Nissolia the extremity of the pod is expanded into a flattened wing; lastly, in the lime, as already mentioned, the fruits drop off in a bunch, and the leaf at the base of the common flower-stalk, or "bract," as it is called, forms the wing.
In Gouania retinaria of Rodriguez the same object is effected in another manner; the cellular tissue of the fruit crumbles and breaks away, leaving only the vascular tissue, which thus forms a net inclosing the seed.
Another mode, which is frequently adopted, is the development of long hairs. Sometimes, as in Clematis, Anemone, Dryas, these hairs take the form of a long, feathery awn. In others the hairs form a tuft
