The North American species of Pholiota, by Alexander H. Smith and L. R. Hesler.

Smith ~ Hesler

21

of the pileus and the subhymenium are gelatinous. This may be said to
be typical for the genus. 2) Those with a dry pileus and dry floccose subhymenium. This is the second largest group. 3) Those in which the
cuticle is gelatinous but the subhymenium is not, as in P. atripes, P.
brunnea, P. innocua, P. pallida and a few others. 4) Those with a nongelatinous pileus epicutis but with a gelatinous subhymenium as in
P. squarrosa, the type of the genus.
Pileus trama. The hyphae composing the trama (context) of the
pileus commonly are disposed either radially or interwoven. In the radial
type, tangential sections reveal the transverse ends of the hyphae suggesting a psueudoparenchyma. A radial section, however, will reveal the true
arrangement and type of element. In the interwoven type, tangential
sections merely show the hyphae interlaced. An intermediate type, radialinterwoven, is not infrequent, and is distinguished by radially-disposed
hyphae, but these hyphae, instead of being parallel, are interwoven. In
some instances, we have described the pileus trama as vesiculose; but
whether this condition results from poorly dried material, or represents
the true structure is not clear. We have not encountered truly amyloid
hyphae in either the pileus cutis or context. However, one reaction we
have observed with Melzer's reagent may have some significance. In a
number of species, when the pileus context was revived in KOH, the
hyphae revived exceptionally well and were seen to have a colloidalappearing content (granular but homogeneous). Sections mounted in
Melzer's show these same hyphae to lhave a cinnabar red to orange yellow
content. This is a very striking reaction but one for which as yet the
significance is not clear. It is the main difference between Pholiota
limonella Peck and P. squarroso-adiposa Lange. However, it is a widespread reaction among the fungi. Smith has observed it in Macowanites
(in the astrogastraceous fungi), in Leccinum, in the Boletaceae, and
here in Pholiota to name the larger groups. In nearly all of these the
very well revived hyphae in KOH with their colloidal-appearing content
enabled the Melzer's reaction to be accurately predicted.
In most species examined, the pileus trama is homogeneous and is
uniform throughout in structure. In P. stratosa, however, it is duplex; the
outer (upper) half being loosely radial-interwoven; the inner (lower)
half compactly radial. In P. acr ocystis, the outer portion is of large
vesiculose elements, and the inner of narrower elements.
Pileus Cuticle. The covering of the pileus in its simplest form is a
more or less undifferentiated surface area-not greatly distinct in structure from that of the context. Examples of species in which the cuticle
is not sharply differentiated include P. angustifolia, anomala, duroides
and scabella. In a slightly more modified dermal layer, surface hyphae
are darker and often with thicker walls than those of the tramal area. In
some species the surface hyphae are repent, and with a few or no erect
to semi-erect hyphae; in such a condition, the pileus is glabrous. In
several species, however, hyphae, often darker brown and in clusters,