The seeds of Sisymbrium officinale are largely heterogeneous in mass and colour within the ripe fruit. In order to initiate the charac-terization of the germinative process from these heterogeneous seeds, we have used two different seed lots (i.e. brown and light-brown), and studied several physical and physiological properties and their possible influence on the germination rate. The most notable features from this work were: (i) the mass of the brown seeds was higher than the light-brown ones, which imbibed more quickly; (ii) light seeds contain much less mucilage (myxospermy) than do the brown; (iii) under optimal germination conditions for the brown seeds, the light-brown ones germinated 6-fold less; and (iv) very similar profiles of germination stimulation was found in the presence of gibberellins (i.e. GA 4+7) and ET in brown seeds, but both hormones were not capable of stimulating the germination in light-brown ones. As a general conclusion, we have demonstrated the coexistence in ripe fruits of S. officinale of two seed lots with remarkable physiological and phy-sical heterogeneity that could be used as a tool to increase our knowledge about the germination process.