A pressure-responsive container assembly and elastically-deformable penetrablecap is provided. Embodiments of the penetrable cap of the present invention include,but are not limited to: an annular sealing portion for engaging an inner surfaceof a container, a substantially rigid portion extending radially inward fromthe annular sealing portion a flexible transition portion extending radiallyinward from the substantially rigid portion and a penetrable portion extendingradially inward from the transition portion for closing the opening definedby the container. Thus, embodiments of the present invention may thus allow thepenetrable portion to elastically deform about the transition portion to a generallyconvex shape so as to exert a radially outward force that may be transmitted bythe substantially rigid portion to the annular sealing portion so as to reinforcea fluid-tight seal between the annular sealing portion and the inner surfaceof the container.
