Abstract:The natural seed coat of Seriphidium transiliense Poljak could indirectly absorb water to almost saturation in 1 to 3 h at different temperatures and different relative humidities (RH). At lower humidifies, temperature almost did not affect the water absorbing rate, but at higher humidities, water absorbency escalated with temperature rise. In drought condition with a RH of 21%, it could still retain 10% of water. The direct water absorbing rate of the natural seed was about 1 500%, while that of the seed without film was only 170%. The natural seed coat made up 11% of the total seed weight. The direct absorbing rate was 12 400%. The water absorbency belonged to monomolecular layer absorption at RH < 70%. The ability of water absorbency was stronger at RH > 70%, and the water absorbency belonged to multimolecular layer absorption. There was a linear correlation between the reciprocal of the water absorbing rate and that of the water absorbing time. According to the classifying analysis and the determination of the seed coat substances using IR, it was initially maintained that the main composition of the seed coat of Seriphidium transiliense Poljak was neither protein, pectine, cellulose, nor starch, but some other polysaccharide composed of aldoses. It also contained a kind of acid-base indicating substance.