 Although A. hygrometricus bears a superficial resemblance to member of the " true earthstars " Geastrum , it may be readily differentiated from most by the hygroscopic nature of its rays . Hygroscopic earthstars include G. arenarium , G. corollinum , G. floriforme , G. recolligens , and G. kotlabae . Unlike Geastrum , the young fruit bodies of A. hygrometricus do not have a columella ( sterile tissue in the gleba , at the base of the spore sac ) . Geastrum tends to have its spore sac opening surrounded by a peristome or a disc , in contrast with the single lacerate slit of A. hygrometricus . There are also several microscopic differences : in A. hygrometricus , the basidia are not arranged in parallel columns , the spores are larger , and the threads of the capillitia are branched and continuous with the hyphae of the peridium . Despite these differences , older specimens can be difficult to distinguish from Geastrum in the field . One species of Geastrum , G. mammosum , does have thick and brittle rays that are moderately hygroscopic , and could be confused with A. hygrometricus ; however , its spores are smaller than A. hygrometricus , typically about 4 µm in diameter . 
 Although A. hygrometricus <a href='uninflect' title='1'><mark>bears</mark></a> a superficial resemblance to member of the " true earthstars " Geastrum , it may be readily differentiated from most by the hygroscopic nature of its rays . Hygroscopic earthstars include G. arenarium , G. corollinum , G. floriforme , G. recolligens , and G. kotlabae . Unlike Geastrum , the young fruit bodies of A. hygrometricus do not have <a href='None' title='2'><mark>a</mark></a><a href='negative_concord' title='3'><mark>columella</mark></a> ( sterile tissue in the gleba , at the base of the spore sac ) . Geastrum <a href='uninflect' title='4'><mark>tends</mark></a> to have its spore sac opening surrounded by a peristome or a disc , in contrast with the single lacerate slit of A. hygrometricus . <a href='dey_it' title='5'><mark>There</mark></a> are also several microscopic differences : in A. <a href='negative_concord' title='6'><mark>hygrometricus</mark></a> , the basidia are not arranged in parallel columns , the spores are larger , and the threads of the capillitia are branched and continuous with the hyphae of the peridium . Despite these differences , older specimens can be difficult to distinguish from Geastrum in the field . One species of Geastrum , G. mammosum , <a href='uninflect' title='7'><mark>does</mark></a> have thick and brittle rays <a href='null_relcl' title='8'><mark>that</mark></a><a href='drop_aux' title='9'><mark>are</mark></a>moderately hygroscopic , and could be confused with A. hygrometricus ; however , its spores are smaller than A. hygrometricus , typically about 4 µm in diameter . 
Although A. hygrometricus bear a superficial resemblance to member of the " tru earthstars " Geastrum , it may be readily differentiated from most by da hygroscopic nature of its rays . Hygroscopic earthstars include G. arenarium , G. corollinum , G. floriforme , G. recolligens , and G. kotlabae . Unlike Geastrum , tdayoung fruit bodies of A. hygrometricus do not have no columella ( sterile tissue in the gleba , at the base of the spore sac ) . Geastrum tend to have its spore sac opening surrounded by a peristome or a disc , in contrast witt the single lacerate slit of A. hygrometricus . It is also several microscopic differences : in A. no hygrometricus , the basidia ain't arranged in parallel columns , the spores are larger , and the threads of thdaapillitia r branched and continuous with thedaphae of the peridium . Despite these differences , older specimens can be difficult to distinguish from Geastrum in the field . One species of Geastrum , G. mammosum , do have thick and brittle rays moderately hygroscopic , and could be confused wit A. hygrometricus ; however , its spores are smaller than A. hygrometricus , typically about 4 µm in diameter .