A cap and a base fit together to form the culture vessel. Adjacent the tops of the walls of the base is a rim which is "L" shaped in cross-section, consisting of a bottom leg joined to the base walls and an upright leg. Downwardly extending walls of the cap project into the space between this flange and the walls of the base. These cap walls have a plurality of spaced ribs which frictionally engage the walls of the base so that the cap will maintain a position in which it is slightly raised above the position wherein the cap is fully seated against the base. When in that raised position a length of cotton filtering material may be used between the bottoms of the cap walls and the bottom leg of the rim. The cap has an outside peripheral flange coplanar with the upright leg thereby permitting pressure sensitive tape to be applied to the two and bridging the space therebetween. Extending downwardly from the top, within the base walls and adjacent thereto, is a condensate drip flange.