 The spores are smooth , spindle @-@ shaped , and measure 13 @.@ 5 – 19 @.@ 8 by 5 @.@ 0 – 7 @.@ 2 µm — rather large for a member of the Boletaceae . <unk> @-@ yellow or greenish yellow when mounted in a dilute potassium hydroxide , they are dextrinoid ( yellowish- or reddish @-@ brown ) when stained with Melzer 's reagent . The basidia ( spore @-@ bearing cells in the hymenium ) are club @-@ shaped , hyaline ( translucent ) , four @-@ spored , and measure 28 @.@ 8 – 42 @.@ 3 by 7 @.@ 2 – 11 @.@ 7 µm . The hymenium contains basidioles ( immature or aborted basidia ) , which are club @-@ shaped and measure 20 @.@ 7 – 35 @.@ 1 by 7 @.@ 2 – 9 @.@ 0 µm . Pleurocystidia ( cystidia on the surface of the tubes ) range in shape from somewhat spindle @-@ shaped to cylindrical , and are hyaline , smooth , and thin @-@ walled , with dimensions of 41 @.@ 4 – 61 @.@ 2 by 7 @.@ 2 – 10 @.@ 8 µm . Cystidia on the edges of the pores ( cheilocystidia ) are 31 @.@ 5 – 49 @.@ 5 by 7 @.@ 2 – 13 @.@ 5 µm , spindle @-@ shaped to centrally swollen , hyaline , smooth , and thin @-@ walled . Clamp connections are absent from the hyphae . 
