A bifurcated stem foam pump is shown for use in foam dispensers. An air compressor portion (18) of the bifurcated pump is attached to and maintained as a portion of the dispenser housing (12). A portion (16) of the pump for transferring liquid and including a portion (50) for generating foam is sealingly attached to and provided as a portion of a replaceable liquid-containing cartridge (14) in the foam dispenser. The two portions (16, 18) mate and form a completed pump assembly operative for generating foam from the liquid of the cartridge when the cartridge is placed within the dispenser housing and the two pump portions are mated. The air compressor portion (18) includes a collar (24) having an air piston (26) reciprocatingly received therein. The collar (24) is attached to the dispenser housing (12). A collar (38) receiving a hollow stem pump (34, 36) is attached to the liquid cartridge. Actuation of the air piston (26) correspondingly actuates the stem pump (34, 36) such that air and liquid are forced together in the stem pump and through the foam generating member (50).