 The fruit body of Suillus sibiricus is a medium @-@ sized bolete . The cap is at first hemispherical and straw yellow , but expands with maturity and finally flattens out becoming darker with reddish brown spots or fibrils . The cap diameter is up to 10 cm ( 3 @.@ 9 in ) . The cap cuticle is mucilaginous especially when moist and can be peeled off . A partial veil extends from the stem to the cap periphery in immature specimens . In mature specimens , it is obliterated leaving a <unk> ring around the stem and fragments hanging from the cap periphery . The tubes are initially yellow but become brown , adnate or slightly decurrent . The pores are angular , wider than 1 mm in diameter and the same colour as the tubes but stain dirty pink or vinaceous when bruised . The tubes that make up the pores are 7 to 10 mm ( 0 @.@ 3 to 0 @.@ 4 in ) long . <unk> can be present and these leave dark brown spots after drying out . 
