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Glossary


APOTHECIUM
An ascocarp in which the hymenium is exposed at maturity. Generally cup- or saucer-shaped, apothecia can also be long and narrow (lirellae).
AREOLATE
Having division by cracks into small areas. Descriptive of a thallus marked off into minute, usually polygonal areas (areoles) like a jigsaw pattern with pieces together or somewhat separated.
ASCOCARP (=ASCOMA)
An ascus-containing fruiting body. Apothecia and perithecia are the most common types of ascocarps associated with lichens.
ASCOSPORES
A spore produced in an ascus. Ascospores are sexual spores. Often diagnostic, in addition to the number of ascospores per ascus, are their shape, size, color, and number of cells.
ASCUS
The sac-like structure in which ascospores are found. They vary in shape from narrow and elongate to nearly round. While the number of ascospores per ascus in usually 8, 1, 2, 4, 6, as well as numerous ascospores per ascus are also known.
ASEXUAL REPRODUCTION
Asexual or vegetative reproduction in lichens may be by 1) simple fragmentation of the thallus, 2) the development of soralia which contain minute powdery propagules (soredia), and 3) the development of numerous small, simple or branched-coralloid, corticate isidia. These methods involve the dissemination of the united mycobiont and photobiont. The position, shape, texture, and color of the soralia and isidia are often diagnostic. A number of species also develop immersed, flask-shaped pycnidia in which numerous, often charateristically-shaped conidia develop. (Conidia are asexual spores)
CEPHALODIA
Minute growths occurring on or within the thallus of many lichens, cephalodia are, in reality, very tiny lichen thalli containing a blue-green alga different from the alga of the host lichen. They vary in size from tiny warty lobules to large fruticose structures. They are known in about 400 lichen species in diverse groups.
CILIA
Hair-like (hyphal) thalline appendages, occurring at the thallus or apothecial margin.
COLLECTION DATA THAT NEEDS TO BE RECORDED
--Pinpoint the exact location of the are being collected (Can someone unfamiliar with the area find the same spot 100 years later?)
--Describe the substrate or name it accurately.
--State the general habitat, e.g., roadside, old field, north-facing slope.
--Record the county, including township and range, and state.
--Always include the collector's name and the date of the collection.
CORTEX
The outer hyphal surface layers of the lichen thallus. The term applies to both the upper and lower surfaces: Upper cortex, lower cortex.
CYPHELLAE
A break in the lower (rarely upper) cortex of a lichen thallus which is roundish or ovate and in section appears cup-like. Exposes medullary hyphae. Characteristics of Sticta.
HOLDFAST
An algal-free thickeded mass of hyphae used for attachment. For example, the organ of attachment of Usnea, old man's beard.
HYMENIUM
The spore-bearing layer of a fruiting body, hte hymenium is composed of the asci (containing the ascospores) intermixed with the sterile hyphae called paraphyses.
HYPHAE
The strands or filaments of the mycelium of a fungus, hyphae are the segmented cells that constitute the body of the mycobiont of a lichen.
HYPOTHALLUS (=PROTHALLUS)
An algal-free white or dark brown to black zone (containing only the mycobiont) sometimes visible between areolae and at the growing margins of crustose lichen thalli. They hypothallus is the first hyphae of the thallus to grow. Hypothallus also describes the spongy (hyphal) tissue on the underside of the thallus of genera like Anzia.
ISIDIA
Small, cylindrical, coralloid or flattened, simple or branched outgrowths from the surface of the thallus. As extrusions of cortical, algal, and medullary tissues, they serve as asexual (or vegetative) reproductive bodies.
LECANORINE APOTHECIA
Apothecia with a thalline margin, i.e., with a border or rim around the central disc that is the same color as the parent thallus. Such a margin is also characterized by containing algal cells.
LECIDEINE APOTHECIA
Apothecia without a thalline margin. If a border or rim is evident around the central disc, it is called a proper margin and will be the color of the disc and not the color of the parent thallus. The margins of such apothecia are without algae.
LICHENS
The lichens are a biological and not a systematic group and each is basically a stable self- supporting association of a fungus (the mycobiont) and an alga (the photobiont). They are unique in that in many (but not all) cases the resulting life form and behavior differ markedly from that of the isolated components.
LIRELLAE
A long, narrow apothecium.
MEDULLA
The loose layer of hyphae below the upper cortex and algal layer.
MYCOBIONT
The fungal component of a lichen, the mycobionts of most lichens (98%) belong to the fungal Subdivision Ascomycotina (the "sac fungi"). Lichenization also occurs in a few members of the fungal Subdivisions Basidiomycotina (the "club fungi") and Deuteromycotina, as well as the enigmatic Geosiphon. Names given to lichens are considered as referring to the mycobiont.
PERITHECIA
An Ascocarp in which the hymenium is enclosed at maturity - lining the bottom of the perithecium on the inside. Perithecia are imbedded to sometimes on the surface of lobes. Compare Pycnidia.
PHOTOBIONT
The photosynthetic symbiont of a lichen which may be a green alga (phycobiont), or a blue-green alga (cyanbiont). Some 37 genera have now been identified as lichen photobionts.
PRUINA (PRUINOSE)
A powdery or frosty bloom on the surface of the thallus or fruiting body.
PSEUDOCYPHELLAE
Tiny, undifferentiated openings (often appearing as small nicks) in the upper or lower cortex through which medullary hyphae often protrudes. They provide valuable taxonomic characters.
PYCNIDIA
Small, flask-shaped structures that are filled with simple or branched hyphae from which bud numerous asexual spores (conidia). They may be confused with perithecia (which contain the sexual ascospores) since they both are immersed in the medulla and open through a pore in the cortex. This pore (or ostiole) appears as a brown to black dot in the upper cortex of the thallus.
RHIZINES
Black to light brown cords of hyphae extending from the lower cortex to the substrate and anchoring the thallus firmly.
THALLUS
The vegetative body of a lichen.
THALLUS CLADONIAEFORM
A form of fruticose lichens in which upright podetia rise above a crustose or squamulous primary thallus. Podetia are simple and unbranched, sparingly branched, or richly blanched and shrublike.
THALLUS CRUSTOSE
Thallus crust-like and wholly or partially developing within the substrate. At times appearing as just a colored stain. If superficial, then appressed and tightly attached, with rhizines absent or minute.
THALLUS FOLIOSE
Thallus "leaf-like", with lobes distinctly formed. Lobes usually broadened and contiguous, independent of each other to crowded and overlapping. Adnate to loosely attached to the substrate by rhizines.
THALLUS FRUTICOSE
Thallus shrub-like or beard-like, fruticose lichens may be erect or pendulous. The branches are cylindrical or strap-shaped and they are often richly branched. They have a radial structure and are attached to the substrate at a single, usually basal, point or are unattached.
THALLUS LEPROSE
Thallus lacking internal organization into cortex, medulla, or algal layers; entirely dissolved into soredia.
THALLUS STRATIFIED (=HETEROMEROUS)
Descriptive of the internal structure of the thallus, a stratified lichen is one in which the photobiont (the alga) is in a compact layer below the upper cortex. Most lichens have a stratified thallus and include crustose, foliose and fruticose growth forms.
THALLUS SQUAMULOSE
A form intermediate between foliose and crustose thalli, a squamulose thallus is one with small, usually overlapping, flattened lobes or scales.
THALLUS UMBILICATE
A form of foliose lichens that is roughly circular in outline and attached to the substrate by a single set of coalescent hyphae. Characteristic of the so-called "rock tripes" in the family Umbilicariaceae.
THALLUS UNSTRATIFIED (=HOMOIOMEROUS)
Descriptive of the internal structure of the thallus, an unstratified lichen is one in which the photobiont (always a blue-green alga) is distributed at random throughout the thallus. Such thalli include crustose, foliose and fruticose growth forms. The term unstratified refers specifically to the internal structure of the gelatinous lichens.
THE GELATINOUS LICHENS
Descriptive of those lichens with an unstratified thallus, the gelatinous lichens are usually dark bluish, slate-colored to black. The dark color is the result of the fact that blue-green algae are intermixed throughout the thallus. In addition to the dark color of the thallus, the gelatinous lichens can also be recognized by the fact that they tend to take on the consistency of moist gelatin when wet.
TOMENTUM (TOMENTOSE)
A mat of short fungal hyphae having a downy or woolly appearance.
SEXUAL REPRODUCTION
Only the mycobiont reproduces sexually, a process culminating in the development of an ascocarp containing ascopores.
SORALIUM
Decorticate portions of a lichen thallus where soredia are located. Usually formed from medullary hyphae thrusting upwards through cracks or pores in the upper cortex. Soralia may be diffuse (the upper surface of the lichen becoming a continuous soredial mass) or delimited (i.e., confined to well-defined areas). Soralia may be laminal (on the surface) or marginal in position and their texture may be farinose (fine or meal-like) or granular.
SOREDIA
Non-corticate combination of photobiont and fungal hyphae having the appearance of powdery granules. Soredia are capable of reproducing a lichen vegetatively. They are generally produced in localized masses called soralia.
SUBSTRATE
The material on which the lichen is growing or to which it is attached. Lichens may be:
Terricolous - growing on the ground
Saxicolous - growing on rocks
Lignicolous - growing on wood
Corticolous - growing on bark
Foliicolous - growing on leaves





Last Updated April 18, 2011
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