Bulletin of the British Museum (Natural History)

LICHEN GENUS MICAREA IN EUROPE 63
tightly bound to hyphae) but such knowledge is sometimes of supplementary value, e.g. when
comparing M. eximia versus M. nigella and M. olivacea versus M. tuberculata.
A more important diagnostic character in Micarea is the colour of the hypothecium in water
mounts, and the corresponding colour changes obtained by the addition of KOH and HNO3. A
discussion of the pigments involved is given under 'chemistry'.
The height of the hypothecium (in vertical section) is largely dependent on the overall size and
(especially in species with a poorly developed excipulum) convexity of the apothecium. The
measurements given in the species descriptions relate to normally developed, non-tuberculate
apothecia. This character is often very variable for a given species and consequently of Uttle
diagnostic value when comparing closely similar species. One exception to this is the case of M.
contexta (20-90 /am) versus M. melaena (80-160 /xm).
In Lugol's iodine the hypothecial tissues are non-amyloid, although there is sometimes a faint
bluing in the vicinity of ascogeneous hyphae (especially in the upper part of the hypothecium).
Excipulum
The size and distinctiveness of the excipulum ('ectal excipulum') in Micarea varies greatly
according to species and the age of the apothecium. In species such as M. cinerea, M. crassipes
(Fig. 4B), A/, peliocarpa, and M. ternaria the excipulum is sufficiently well developed that their
young apothecia are often weakly or distinctly (M. crassipes) marginate in outward appearance.
However, even when well developed and initially distinct, the excipulum may become reflexed
and ± occluded as the apothecium expands and increases in convexity (Fig. 3A-B) or becomes
tuberculate (Fig. 3C). In many species the excipulum is always extremely reduced or absent
(Fig.4A).
When present, the excipulum is composed of outwardly radiating branched and anastomosing
hyphae that ± separate in K. The hyphae closely resemble paraphyses, but are usually more
dense and more richly branched. With markedly convex apothecia it can be difficult to
distinguish between reflexed portions of the hymenium and what might be an excipulum. In such
cases the excipulum (if present) can be identified in good thin sections by the absence of asci and
a negative (non-amyloid) reaction to Lugol's iodine. The excipulum often differs in colour or
colour intensity from the hymenium, although a similar colour difference may sometimes be
shown by reflexed parts of the hymenium.
In M. crassipes and rare forms of M. lignaria ('f. gomphillaced') the excipular and hypothecial
tissues become vertically extended to form a stipe (Figs 3E, 4B).
Anamorphs (conidial states)
With a few noteworthy exceptions, such as Lindsay (1859, 1872) and Gliick (1899), the conidial
states (anamorphs) of lichenized fungi have received little detailed attention from taxonomists.
Several recent monographic studies have shown that anamorphs can provide useful characters at
various hierarchial levels of classification and the reader is referred to Vobis (1980) and Vobis &
Hawksworth (1981) for further background information on the conidial states of lichens.
Within the genus Micarea there is a diverse array of anamorphic forms, possibly unrivalled by
any other genus of lichens, except perhaps for some of the genera in the Asterothyriaceae
(Vezda, 1979) . Information gained from the study of anamorphs has proved invaluable to me for
the delimitation of species in Micarea; indeed, several species frequently occur without
apothecia but with numerous pycnidia, such that a detailed knowledge of the latter is often
essential for their identification (see 'key to species without apothecia').
Conidiomata
The conidiomata are usually pycnidial, and are globose, ovoid, doliiform, or ceriberiform in
shape. They may be immersed (or partly so) within the thallus or substratum, sessile, or borne
on stalks (pycnidiophores). When stalked, the pycnidia are usually ± doliiform and the
stalk-tissue is comprised of loosely interwoven hyphae bound by a gel matrix which is often
pigmented. In addition, the 'stalk-part' often includes effete pycnidia (Fig. 35B-D). The stalks
are sometimes branched due to the simultaneous development of two (or more) pycnidia at the