The veiled species of Hebeloma in the western United States / Alexander H. Smith, Vera Stucky Evenson, and Duane H. Mitchel.

14

The Veiled Species of Hebeloma

used in conjunction with other characters to distinguish species. With
such spores an oil-immersion objective of NA 2.5, 3, or 4 will be a
distinct help. Whether or not spore ornamentation in subgenus Hebeloma is the key to the phylogeny of the species appears debatable. But
until we have subjected all species to SEM studies, there is little use in
defending any one position.
It appears (see pls. 9-12) that the spore has a thin outer layer
over it that in the late stages of spore maturation ~ disintegrates, or at
least is pulled apart (either by the shrinking of the layer itself, or is
broken up by the increase in size) as the spore matures. It should be
pointed out here that the smooth-spored species (H. evensoniae) is
atypical in the genus Hebeloma both as far as spore ornamentation and
the content of the cheilocystidia are concerned.
The dextrinoid character of the spores deserves further comment.
30
23
Figs. A28-32. Terminology of Cuticular and Hypodermial Layers of the Pileus:
fig. 28, a simple cutis if slime is not present; fig. 29, the presence of slime (indicated by
stippling) makes it an ixocutis; fig. 30, a trichodermium or "turf," (if slime is present in
the layer it is termed an ixotrichodermium); fig. 31, a short section of a cellular hypodermium (the cells are ~ isodiametric); fig. 32, a type of hypodermium intermediate between cellular and hyphoid (some of the component cells are elongated and some +
isodiametric). In a "hyphoid" hypodermium the hyphal cells are predominantly much
longer than wide.
The term ixolattice has been used in places in the text. It is a layer of copious
slime with cuticular hyphae scattered through it. It may originate in cases where the
ixotrichodermium consists of exceptionally long elements and these collapse into a layer
as the slime dries. It is to be expected also in old caps featuring an ixocutis in which the
hyphae have become widely separated because of the copious slime.