Two different pn annihilation modes, (p) over barn --> pi (-)4 pi (0) and (
p) over barn --> 2 pi (-)2 pi (0)pi (+), are used to study the 4 pi -decays
of scalar and vector mesons. The data are dominated by 4 pi scalar isoscal
ar interactions. At least two states are needed, the f(0)(1370) and the f(0
)(1500). The 4 pi -decay width of the f(0)(1370) is more than 6 times large
r than the sum of all observed partial decay widths to two pseudoscalar mes
ons. The state has important couplings to (pi pi )s(pi pi )s and to pp. The
4 pi -decays of the f(0)(1500) represent about half of its total width. Th
e p(1450) and the p(1700) are observed in several 4 pi decay modes. The rat
io of the 4 pi relative to the 2 pi decay of the p(1450) is in contradictio
n to its proposed interpretation as a pure hybrid state but it suggests tha
t it is not a pure 2(3)S(1)-state either. Our results favour the assignment
of the p(1700) as D-3(1) state, its interpretation as 3(3)S(1)-state is le
ss plausible.