The
thallus of
Malmidea lichens grow on bark (
corticolous) or on leaves (
foliicolous). The form of the thallus is like a
crust, ranging in surface texture from smooth to (studded with wartlike protuberances), (covered with small grains) or (covered with pustules). These variously shaped surface bumps are often formed by (spherical aggregations of
photobiont cells surrounded by short-celled
hyphae) that develop on a whitish fibrous underlying
prothallus. The partner of
Malmidea is a member of
Chlorococcaceae, a family of
green algae.
Malmidea apothecia are
sessile, with a more or less rounded shape, and have a distinct margin. They have a form, meaning that they have only a pale, not blackened proper margin and always lack a margin on the thallus. The is usually (a cell arrangement where the hyphae are oriented in all directions), made of radiating
hyphae, partly with medullary layer or chambers composed of loosely arranged, periclinal hyphae (i.e. lined up in parallel adjacent to another layer of hyphae) with constricted
septa and incrusted with
hydrophobic granules. The (the layer of hyphal tissue immediately beneath the hymenium) is (a cell arrangement where the hyphae are all oriented in one direction), and translucent to dark brown.
Asci are club-shaped, lacking a distinct tubular structure in the that is characteristic of family Ectolechiaceae.
Ascospores usually number four to eight per ascus, and are colourless,
ellipsoid, non-
septate, and usually filled with oblong crystals. The spore walls are evenly thickened or thickened at the ends, and (having a transparent outer layer).
Conidia are threadlike and curved, measuring 17–25 by 0.8 μm.
Pycnidia are rare in this genus; they occur in the thallus warts and are whitish and spherical, about 0.1 mm in diameter. ==Chemistry==