This section is from the book "Studies of American Fungi: Mushrooms, Edible, Poisonous, Etc.", by George Francis Atkinson. Also available from Amazon: Studies of American Fungi: Mushrooms, Edible, Poisonous, Etc..
This species is also related to the frondose polyporus, but is very distinct. It is more erect, the branching more open, and the caps at the ends of the branches are more or less circular and umbilicate. The branches are long, cylindrical and united near the base. The spreading habit of the branching, or the form of the caps, suggests an umbel or umbrella, and hence the specific name umbellatus.
Polyporus umbellatus. Caps hair-brown (natural size, often much larger). Copyright.
The tufts occur from 12-20 cm. in diameter, and the individual caps are from 1-4 cm. in diameter. It grows from underground roots and about stumps during summer. It is probably edible, but I have never tried it. Figure 183 is from a plant (No. 1930, C. U. herbarium) collected in Cascadilla woods, Ithaca.
Polyporus sulphureus ( Bull. ) Fr. Edible. (Boletus caudicinus Schaeff. T. 131, 132: Polyporus caudicinus Schroeter, Cohn's Krypt. Flora, Schlesien, p. 471, 1899). - The sulphur polyporus is so-called because of the bright sulphur color of the entire plant. It is one of the widely distributed species, and grows on dead oak, birch, and other trunks, and is also often found growing from wounds or knotholes of living trees of the oak, apple, walnut, etc. The mycelium enters at wounds where limbs are broken off, and grows for years in the heart wood, disorganizing it and causing it to decay. In time the mycelium has spread over a considerable area, from which nutriment enough is supplied for the formation of the fruiting condition. The caps then appear from an open wound when such an exit is present.
The color of the plant is quite constant, but varies of course in shades of yellow to some extent. In form, however, it varies greatly. The caps are usually clustered and imbricated, that is, they overlap. They may all arise separately from the wood, and yet be overlapping, though oftener several of them are closely joined or united at the base, so that the mass of caps arises from a common outgrowth from the wood as shown in Fig. 184. The individual caps are flattened, elongate, and more or less fan-shaped. When mature there are radiating furrows and ridges which often increase the fan-like appearance of the upper surface of the cap. Sometimes also there are more or less marked concentric furrows. The caps may be convex, or the margin may be more or less upturned so that the central portion is depressed. When young the margin is thick and blunt and of course lighter in color, but as the plant matures the edge is usually thinner.
In some forms of the plant the caps are so closely united as to form a large rounded or tubercular mass, only the blunt tips of the individual caps being free. This is well represented in Fig. 185, from a photograph of a large specimen growing from a wound in a butternut tree in Central New York. The plant was 30 cm. in diameter. The plants represented in Plate 69 grew on an oak stump. The tree was affected by the fungus while it was alive, and the heart wood became so weakened that the tree broke, and later the fruit form of the fungus appeared from the dead stump.
The tubes are small, and the walls thin and delicate, and are sometimes much torn, lacerated, and irregular. When the mycelium has grown in the interior of a log for a number of years it tends to grow in sheets along the line of the medullary rays of the wood or across in concentric layers corresponding to the summer wood. Also as the wood becomes more decomposed, cracks and rifts appear along these same lines. The mycelium then grows in abundance in these rifts and forms broad and extensive sheets which resemble somewhat chamois skin and is called "punk." Similar punk is sometimes formed in conifers from the mycelium of Fomes pinicola.
Plate 69, Figure 184
Polyporus sulphureus, on oak stump. Entirely sulphur-yellow (1/6 natural size). Copyright.
Plate 70, Figure 185 - Polyporus sulphureus. Caps joined in a massive tubercle (1/2 natural size).
Polyporus sulphurcus has long been known as an edible fungus, but from its rather firm and fibrous texture it requires a different preparation from the fleshy fungi to prepare it for the table, and this may be one reason why it is not employed more frequently as an article of food. It is common enough during the summer and especially during the autumn to provide this kind of food in considerable quantities.