1. An integral, temporary, portable, legless seat of relatively thin plastic material constructed to be (a) readily supported at end portions thereof by and on seat portions of selected, spacedapart, substantially aligned armless chairs without requiring fastening means and (b) readily removed and stacked in substantially nesting relationship with another temporary seat of substantially the same construction, which temporary, legless seat comprises a substantially planar and substantially horizontal seat portion which has restricted yieldability under load, is longer than it is wide, has a length sufficient for seating at least one person while substantially planar and substantially horizontal end portions of said seat portion are supported by and on said seat portions of selected, spaced-apart, substantially aligned armless chairs, and has a width substantially conforming to the width of said seat portions of said supporting chairs, the front of said substantially planar and substantially horizontal seat portion having a downturned depending lip portion which extends along its length and is shaped at its opposed end portions for being positioned approximately contiguous to front portions of seat portions of said supporting chairs, the back of said substantially planar and substantially horizontal seat portion having an upstanding lip portion which extends along its length and is shaped to restrict the movement backward of a person sitting on said temporary seat, said lip portions enhancing the supporting strength of said temporary seat under load.

5. The combination of a temporary, portable seat constructed of relatively thin material which is supported at opposed end portions thereof by and between seat portions of spaced-apart, substantially aligned chairs, said temporary seat being constructed to be (a) readily supported at end portions thereof by and on seat portions of said spaced-apart chairs without requiring fastening means and (b) readily removed from said supporting chairs and stacked in substantially nesting relationship with another temporary seat of substantially the same construction, said temporary seat having a substantially planar and substantially horizontal seat portion which has restricted yieldability under load, is longer than it is wide, has a length sufficient for seating at least one person while said substantially planar and substantially horizontal end portions of said seat portion are supported by and on said seat portions of said spaced-apart chairs, and has a width substantially conforming to the width of said seat portions of said supporting chairs the front of said seat portion of said temporary seat having a downturned depending lip portion constructed for being positioned approximately contiguous to front portions of seat portions of said supporting chairs, the back of said seat portion of said temporary seat having an upstanding lip portion which is shaped to restrict the movement backward of a person sitting on said temporary seat.

10. The combination of an integral, temporary, portable, legless seat supported at opposed end portions thereof by and between seat portions of spaced-apart, substantially aligned, armless chairs, said temporary seat being of relatively thin plastic material constructed to be (a) readily supported at end portions thereof by seat portions of said spaced-apart chairs and (b) readily removed from said supporting chairs and stacked in substantiAlly nesting relationship with another temporary seat of substantially the same construction, said temporary seat having a substantially planar seat portion which has restricted yieldability under load, is longer than it is wide, has a length sufficient for seating at least one person while said end portions of said seat portion are supported by said spaced-apart chairs, and has a width substantially conforming to the width of said seat portions of said supporting chairs, the front of said substantially planar seat portion having a downturned depending lip portion which extends along its length and is constructed for being positioned approximately contiguous to front portions of said supporting chairs, the back of said substantially planar seat portion having an upstanding lip portion which extends along its length and is shaped to restrict the movement backward of a person sitting on said temporary seat, said lip portions enhancing the supporting strength of said temporary seat under load.