The fungi with pores naturally divide into two groups. The perishable fleshy fungi with pores easily separating from the cap and from each other make the family Boletaceae. The perishable fleshy fungi, and the leathery, corky, membranous or woody fungi, with pores permanently united to the cap and to each other, make up the family Poly-poraceae. In each the spores are borne on the linings of pores or tubes placed close together, so that on the surface of the cap they look much like large pin pricks on a stiff cushion ; but in a sectional view, obtained by cutting the cap from the upper surface to the lower, they look like tubes placed side by side.
Among the fleshy forms the genus Fistulina has the stem lateral and the tubes close together, but distinct from each other. The genus Boletus has the tubes easily separable from the cap, and the genera Boletinus and Strobilomyces have the tubes quite firmly connected. A brief comparison of essential points is given in the table.
1. Stem strictly lateral. Mouths of the tubes separated from each other............. ...... Genus Fistulina
2. Stem central. Pores readily separating from the cap...Genus Boletus
3. Stem central or eccentric ; fleshy. Pores in more or less radiating rows................. Genus Boletinus
4. Stem central, tough. Pores uniform. Cap woody... Genus Strobilomyces