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The effect of humidity change on spore release of the Nematodontae Polytrichaceae has never been tested experimentally. Similarly, the impact of humidity alterations on structure of the peristome have never been studied.Polytrichum commune Hedw. var. commune from Guizhou Province, China, was selected as the research object to examine effects of simulated wind in the laboratory. By controlling humidity and wind, the mechanism of spore dispersal was revealed.When humidity increased, the size of the peristome and epiphragm enlarged significantly (the peristome has no obvious spatial displacement, unlike the hygroscopic movement of Arthrodontae mosses. Thus, we named it 'sub‐hygroscopic movement'), then recovered to normal size when humidity decreased. When humidity was controlled and wind applied, the scattering of spores gradually decreased as the capsule dried out and finally reached a very low level; when the capsule was wetted or rewetted, the amount of spores released rose and returned to the initial state. Through comparison of moist and dry capsules, only enhanced humidity of the sporophytes led to increases in spore release.The results show that the dispersal of spores was significantly improved in windy conditions and the sub‐hygroscopic movement of the capsule peristome, which ensure the continuity and effectiveness of P. commune reproduction. [ABSTRACT FROM AUTHOR]