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
Passum sub iugum Passum sub iugum The passum sub iugum ("pass under the yoke") was a practice in ancient Italy where defeated enemies were made to pass beneath a yoke constructed of spears either to humiliate them or to remove blood guilt. The practice of "passum sub iugum" was a ritual humiliation of enemies practiced by the people of ancient Italy. Both the Romans and the Samnites forced the captives of their defeated enemies to pass under a yoke formed from spears. The practice is said to have originated as a form of expiation. According to Livy, Horatius killed his own sister because