Malmidea allobakeri is a crustose lichen with a continuous
thallus that is 40–70
μm thick. The surface of the thallus is , with measuring 0.075–0.1 mm in height and 0.07–0.1 mm in width. The thallus has a dull appearance, showing shades of greenish-grey to brownish, and is devoid of
soralia and
isidia (reproductive
propagules). The
medulla, both of the verrucae and the thallus, is white to faintly yellow and reacts to a solution of
potassium hydroxide (i.e., the K
spot test) with an orange to reddish colour. The lichen hosts a (
green algal) photobiont, whose cells measure 6–8 μm in diameter. The
apothecia of
Malmidea allobakeri are
sessile and rounded, measuring 0.3–0.8 mm in diameter and 0.2–0.3 mm in height. The apothecial are plane to slightly convex and range in colour from dark chocolate brown to blackish. The , of the
granifera type, is initially but becomes as the lichen ages and may partly or entirely vanish. It is cream-coloured to greyish or black in colour. The excipulum is hyaline at the periphery and internally contains pockets of the medullary layer filled with greyish to ochraceous-yellow
hydrophobic granules. These granules are opaque and only partially dissolve in potassium hydroxide solution, resulting in a K+ orange-yellowish to greenish lemon-yellow reaction. The is approximately 25 μm high and light brown, while the centrally located is 80–100 μm high, narrowing towards the margin, and dark brown with no reaction to K tests. The of this species is indistinct, and the hymenium is hyaline, measuring 90–110 μm in height. The
asci are sized 70–80 μm by 15–20 μm, containing 6 (occasionally up to 8) non-
septate, ,
ellipsoid ascospores per ascus, measuring 10–14 by 7–8 μm, with a of 1–1.5 μm. Chemically,
Malmidea allobakeri is characterised by the presence of several unidentified
xantholepinones, distinct from those found in
Malmidea bakeri, and it lacks
atranorin. ==Habitat and distribution==