Sedge and alfalfa were inoculated with two lactic acid bacteria, rods and cocci, and incubated at two temperatures, 30 and 43 °C, in small laboratory silos. One percent sucrose was added to alfalfa in one experiment. It was found that bacterial modulation spectacularly increased the acidification of sedge, bur had little effect on alfalfa. The addition of sucrose greatly aided acidification in alfalfa. At 43 °C only cocci survived, indicating their role in acidification of silage. The possibility of bacterial specialization for growth on particular silages and the value of isolates from such silages are pointed out.