However, efforts to demonstrate such enzymes in coconut or Cuphea, which could explain their abundant production of medium-chain fatty acids, have met with little success. Pollard et al. (1991) achieved the breakthrough finding that validated this hypothesis. They examined the California bay tree, which produces over 75% decanoic and lauric acids in its seed TAG. A very active 12:0-ACP thioesterase was found, which could be separated from the ubiquitous 18:1-ACP thioesterase (Pollard et al., 1991). Thus, California bay clearly has two acyl-ACP thioesterases with dif¬ferent substrate specificity; subsequent studies of several other oilseed species have revealed similar medium-chain thioesterases (Davies, 1993; Dormann et al, 1993).