Seed are sometimes sold commercially while still enclosed within the hard wall of the fruit, which must be split open to reach the seed. Different groups of plants have other modifications, the so-called stone fruits (such as the peach) have a hardened fruit layer (the endocarp) fused to and surrounding the actual seed. Nuts are the one-seeded, hard-shelled fruit of some plants with an indehiscent seed, such as an acorn or hazelnut. Seeds are produced in several related groups of plants, and their manner of production distinguishes the angiosperms ("enclosed seeds") from the gymnosperms ("naked seeds"). Angiosperm seeds are produced in
Bird food plants sour or aromatic fruits, distasteful to human beings, even better than the cultivated kinds. Many of these bird-attracting plants are ornamental as well, since many have pretty fruits, red in color and often clinging to their branches far into the winter, furnishing grateful additions to the meager fare of hard-weather birds. The many sparrows feed chiefly on weed seeds, but more acceptable plants from the gardener's point of view can be offered to them: Wild ducks are attracted by several aquatic and semi-aquatic plants, among the most important being: Bird food plants Bird food plants are certain trees, shrubs and