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
Sub-provincial division other, regular prefecture-level divisions, which are completely ruled by their provinces. However, they are marked the same as other provincial capitals (or prefecture-level city if not provincial capital) in almost all maps. The original 16 municipalities were renamed as sub-provincial municipalities on 25 February 1994 by the Central Organization Committee out of prefecture-level municipalities. They are mostly the capitals of the provinces in which they are located. Currently, there are 15 sub-provincial municipalities after Chongqing was designated direct-control: Chongqing was formerly a sub-provincial municipality of Sichuan until 14 March 1997, when it was made an independent municipality by splitting it