White Tulip was an individual who wore a white tulip in his lapel.
Along with Black Rose, White Tulip tried to take Isaac's music. Their first attempt failed, as Isaac had given it to Sarah Jane Smith for safekeeping.
Later, they invaded the Third Doctor's laboratory. The Doctor tried to stop them, but they overpowered him and took the music. (PROSE: An Overture Too Early)
Black Rose and White Tulip later attacked the Eighth Doctor in his TARDIS. (PROSE: DS Al Fine)