While activity generally depended upon lipophilicity(possibly reflecting relative penetration of the caryopsis cuticle[15]), a test homogeneity of regression coefficients between the alcohol and carboxylic acid series(Fig. 1, inset) indicated that the nature of the functional group modulated the dormancy-breaking response. Consistent with idea, relative hydrophobicity was poorly correlated with activity(Fig. 2). If derivatives were eliciting a response in the same way, highly significant correlations should have been obtained(3). In addition, butane, propane, and carbon monoxide were inactive at concentrations expected to stimulate 50% germination or greater based upon their lipophilicities. Low mol wt alkanes are also inactive as a dormancy-breaking substances of Portulaca oleracea(23) and Lactuca sativa(1). Therefore, reason able lipophilicity alone is insufficient to confer a substance with dormancy-breaking activity. The lack of response to CO also suggests that the dormancy-breaking capabilities of weak acids are not a function of metal chelation.