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..
Of the few genera in the Polyporaceae which are fleshy and putrescent, Boletus contains by far the largest number of species. The entire plant is soft and fleshy, and decays soon after maturity. The stratum of tubes on the under side of the cap is easily peeled off and separates as shown in the portion of a cap near the right hand side of Fig. 169. In the genus Polyporus the stratum of tubes cannot thus be separated. In the genera Strobilomyces and Boletinus, two other fleshy genera of this family, the separation is said to be more difficult than in Boletus, but it has many times seemed to me a "distinction without a difference."
The larger number of the species of Boletus grow on the ground. Some change color when bruised or cut, so that it is important to note this character when the plant is fresh, and the taste should be noted as well.
Boletus edulis Bull. Edible. [Ag. bulbosus Schaeff. Tab. 134, 1763. Boletus bulbosus (Schaeff.) Schroeter. Conn's Krypt, Flora. Schles-ien, p. 499, 1889]. - This plant, which, as its name implies, is edible, grows in open woods or their borders, in groves and in open places, on the ground. It occurs in warm, wet weather, from July to September. It is one of the largest of the Boleti, and varies from 5-12 cm. high, the cap from 8-25 cm. broad, and the stem 2-4 cm. in thickness.
The pileus is convex to expanded, smooth, firm, quite hard when young and becoming soft in age. The color varies greatly, from buff to dull reddish, to reddish-brown, tawny-brown, often yellowish over a portion of the cap, usually paler on the margin. The flesh is white or tinged with yellow, sometimes reddish under the cuticle. The tubes are white when young and the mouths are closed (stuffed), the lower surface of the tubes is convex from the margin of the cap to the stem, and depressed around the stem, sometimes separating from the stem. While the tubes are white when young, they become greenish or greenish-yellow, or entirely yellow when mature. The spores when caught on paper are greenish-yellow, or yellow. They are oblong to fusiform, 12-15µ long. The stem is stout, even, or much enlarged at the base so that it is clavate. The surface usually shows prominent reticulations on mature plants near the tubes, sometimes over the entire stem. This is well shown in Fig. 164 from plants (No. 2886, C. U. herbarium) collected at Ithaca, N. Y.
Plate 56, Figure 164
Boletus edulis. Cap light brown, tubes greenish yellow or yellowish; stem in this specimen entirely reticulate (natural size, often larger). Copyright.
Plate 57, Figure 165
Cap light brown, lubes greenish yellow or yellowish; stem in these specimens not reticulate (2/3 natural size). Copyright.
Figure 165 represents plants (No. 4134, C. U. herbarium) collected at Blowing Rock, N. C, in September, 1899. The plant is widely distributed and has long been prized as an esculent in Europe and America. When raw the plant has an agreeable nutty taste, sometimes sweet. The caps are sometimes sliced and dried for future use. It is usually recommended to discard the stems and remove the tubes since the latter are apt to form a slimy mass on cooking.
Boletus felleus Bull. Bitter - This is known as the bitter boletus, because of a bitter taste of the flesh. It usually grows on or near much decayed logs or stumps of hemlock spruce. It is said to be easily recognized by its bitter taste. 1 have found specimens of a plant which seems to have all the characters of this one growing at the base of hemlock spruce trees, except that the taste was not bitter. At Ithaca, however, the plant occurs and the taste is bitter. It is one of the large species of the genus, being from 8-12 cm. high, the cap 7-20 cm. broad, and the stem 1-2.5 cm. in thickness.
The pileus is convex becoming nearly plane, firm, and in age soft, smooth, the color varying from pale yellow to various shades of brown to chestnut. The flesh is white, and where wounded often changes to a pink color, but not always. The tubes are adnate, long, the under surface convex and with a depression around the stem. The tubes are at first white, but become flesh color or tinged with flesh color, and the mouths are angular. The stem is stout, tapering upward, sometimes enlarged at the base, usually reticulated at the upper end, and sometimes with the reticulations over the entire surface (Fig. 166). The color is paler than that of the cap. The spores are oblong to spindle-shaped, flesh color in mass, and single ones measure 12-18x4-5 µ.
The general appearance of the plant is somewhat like that of the Boletus edulis, and beginners should be cautioned not to confuse the two species. It is known by its bitter taste and the flesh-colored tubes, while the taste of the B. edulis is sweet, and the tubes are greenish-yellow, or yellowish or light ochre.
Plate 55 represents three specimens in color.
Boletus scaber Fr. Edible. - This species is named the rough-stemmed boletus, in allusion to the rough appearance given to the stem from numerous dark brown or reddish dots or scales. This is a characteristic feature, and aids one greatly in determining the species, since the color of the cap varies much. The cap is sometimes whitish, orange red, brown, or smoky in color. The plant is 6-15 cm. high, the cap 3-7 cm. broad, and the stem 8-12 mm. in thickness.
The pileus is rounded, becoming convex, smooth, or nearly so, sometimes scaly, and the flesh is soft and white, sometimes turning slightly to a reddish or dark color where bruised. The tubes are small, long, the surface formed by their free ends is convex in outline, and the tubes are depressed around the stem. They are first white, becoming darker, and somewhat brownish. The stem is solid, tapering somewhat upward, and roughened as described above.
The plant is one of the common species of the genus Boletus. It occurs in the woods on the ground or in groves or borders of woods in grassy places. Writers differ as to the excellence of this species for food; some consider it excellent, while others regard it as less agreeable than some other species. It is, at any rate, safe, and Peck considers it "first-class."
Boletus retipes B. & C. - This species was first collected in North Carolina by Curtis, and described by Berkeley. It has since been reported from Ohio, Wisconsin, and New England (Peck, Boleti of the U. S.). Peck reported it from New York in the 23d Report, N. Y. State Mus., p. 132. Later he recognized the New York plant as a new species which he called B. ornatipes (29th Report, N. Y. State Mus., p. 67). I collected the species in the mountains of North Carolina, at Blowing Rock, in August, 1888. During the latter part of August and in September, 1899, I had an opportunity of seeing quite a large number of specimens in the same locality, for it is not uncommon there, and two specimens were photographed and are represented here in Fig. 167. The original description published in Grevillea 1: 36, should be modified, especially in regard to the size of the plant, its habit, and the pulverulent condition of the pileus. The plants are 6-15 cm. high, the cap 5-10 cm. broad, and the stem 0.5-1.5 cm. in thickness.
Plate 58, Figure 166
Boletus felleus. Cap light brown, tubes flesh color, stem in this specimen entirely reticulate (natural size, often larger). Copyright.
The pileus is convex, thick, soft and somewhat spongy, especially in large plants. The cap is dry and sometimes, especially when young, it is powdery; at other times, and in a majority of cases according to my observations, it is not powdery. It is smooth or minutely tomentose, sometimes the surface cracked into small patches, but usually even. The color varies greatly between yellowish brown to olive brown, fuliginous or nearly black. The tubes are yellow, adnate, the tube surface plane or convex. The spores are yellowish or ochraceous, varying somewhat in tint in different specimens. The stem is yellow, yellow also within, and beautifully reticulate, usually to the base, but sometimes only toward the apex. It is usually more strongly reticulate over the upper half. The stem is erect or ascending.
Boletus retipes. Cap yellowish brown, to olive-brown or nearly black, stem yellow, beautifully reticulate, tubes yellow (natural size). Copyright.
The plant grows in woods, in leaf mold or in grassy places. It is usually single, that is, so far as my observations have gone at Blowing Rock. Berkeley and Curtis report it as cespitose. 1 have never seen it cespitose, never more than two specimens growing near each other.
Boletus ornatipes Pk., does not seem to be essentially different from B. retipes. Peck says (Boleti U. S., p. 126) that "the tufted mode of growth, the pulverulent pileus and paler spores separate this species" (retipes) "from the preceding one" (ornatipes). Inasmuch as I have never found B. retipes tufted, and the fact that the pileus is not always pulverulent (the majority of specimens I collected were not), and since the tint of the spores varies as it does in some other species, the evidence is strong that the two names represent two different habits of the same species. The tufted habit of the plants collected by Curtis, or at least described by Berkeley, would seem to be a rather unusual condition for this species, and this would account for the smaller size given to the plants in the original description, where the pileus does not exceed 5 cm. in diameter, and the stem is only 5 cm. long, and 6-12 mm. in thickness. Plants which normally occur singly do on some occasions occur tufted, and then the habit as well as the size of the plant is often changed.
A good illustration of this I found in the case of Boletus edulis during my stay in the North Carolina mountains. The plant usually occurs singly and more or less scattered. I found one case where there were 6-8 plants in a tuft, the caps were smaller and the stems in this case considerably longer than in normal specimens. A plant which agrees with the North Carolina specimens I have collected at Ithaca, and so I judge that B. retipes occurs in New York.