Evolutionary history of plants seed model is shared by basically all gymnosperms (literally: "naked seeds"), most of which encase their seeds in a woody cone or fleshy aril (the yew, for example), but none of which fully enclose their seeds. The angiosperms ("vessel seeds") are the only group to fully enclose the seed, in a carpel. Fully enclosed seeds opened up a new pathway for plants to follow: that of seed dormancy. The embryo, completely isolated from the external atmosphere and hence protected from desiccation, could survive some years of drought before germinating. Gymnosperm seeds from the Late Carboniferous have been found to contain
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