Editing Ascomycota (section)

== Morphology ==
[[File:Ophiocordyceps caloceroides.jpg|thumb|right| A member of the genus ''[[Ophiocordyceps]]'' which is parasitic on arthropods. Note the elongated stromata. Species unknown, perhaps ''Ophiocordyceps caloceroides''.]]
[[File:04 01 02 life cycle Ascomycota, ascus (M. Piepenbring).svg|thumb|Ascomycete life cycle]]
Most species grow as filamentous, microscopic structures called [[hypha]]e or as budding single cells (yeasts). Many [[Anastomosis|interconnected]] hyphae form a [[thallus]] usually referred to as the [[mycelium]], which—when visible to the naked eye (macroscopic)—is commonly called [[Mold (fungus)|mold]]. During sexual reproduction, many Ascomycota typically produce large numbers of [[ascus|asci]]. The ascus is often contained in a multicellular, occasionally readily visible fruiting structure, the [[ascocarp]] (also called an ''ascoma''). Ascocarps come in a very large variety of shapes: cup-shaped, club-shaped, potato-like, spongy, seed-like, oozing and pimple-like, coral-like, nit-like, golf-ball-shaped, perforated tennis ball-like, cushion-shaped, plated and feathered in miniature ([[Laboulbeniales]]), microscopic classic Greek shield-shaped, stalked or sessile. They can appear solitary or clustered. Their texture can likewise be very variable, including fleshy, like charcoal (carbonaceous), leathery, rubbery, gelatinous, slimy, powdery, or cob-web-like. Ascocarps come in multiple colors such as red, orange, yellow, brown, black, or, more rarely, green or blue. Some ascomyceous fungi, such as ''Saccharomyces cerevisiae'', grow as single-celled yeasts, which—during sexual reproduction—develop into an ascus, and do not form fruiting bodies.
[[File:Xylaria hypoxylon.jpg|thumb|left|The "candlesnuff fungus" in its asexual state, ''[[Xylaria hypoxylon]]'']]

In [[lichen]]ized species, the thallus of the fungus defines the shape of the [[symbiosis|symbiotic]] colony. Some [[Phenotypic switching|dimorphic]] species, such as ''[[Candida albicans]]'', can switch between growth as single cells and as filamentous, multicellular hyphae. Other species are [[pleomorphism (microbiology)|pleomorphic]], exhibiting asexual (anamorphic) as well as a sexual (teleomorphic) growth forms.

Except for lichens, the non-reproductive (vegetative) mycelium of most ascomycetes is usually inconspicuous because it is commonly embedded in the substrate, such as soil, or grows on or inside a living host, and only the ascoma may be seen when fruiting. [[Pigment]]ation, such as [[melanin]] in hyphal walls, along with prolific growth on surfaces can result in visible mold colonies; examples include ''[[Cladosporium]]'' species, which form black spots on bathroom caulking and other moist areas. Many ascomycetes cause food spoilage, and, therefore, the pellicles or moldy layers that develop on jams, juices, and other foods are the mycelia of these species or occasionally [[Mucoromycotina]] and almost never [[Basidiomycota]]. [[Sooty mold]]s that develop on plants, especially in the tropics are the thalli of many species.{{Clarify|many ascomycetous species?|date=September 2009}}
[[File:Smardz-Morchella-Ejdzej-2006.jpg|thumb|right|179px|The ascocarp of a [[Morchella|morel]] contains numerous apothecia.]]

Large masses of yeast cells, asci or ascus-like cells, or conidia can also form macroscopic structures. For example. ''[[Pneumocystis]]'' species can colonize lung cavities (visible in x-rays), causing a form of [[pneumonia]].<ref>{{cite journal |vauthors= Krajicek BJ, Thomas CF Jr, Limper AH |year=2009 |title=''Pneumocystis'' pneumonia: current concepts in pathogenesis, diagnosis, and treatment |journal=Clinics in Chest Medicine |volume=30|issue=2|pages=265–89|pmid=19375633 |doi= 10.1016/j.ccm.2009.02.005 }}</ref> Asci of ''[[Ascosphaera]]'' fill [[honey bee]] [[larva]]e and [[pupa]]e causing mummification with a chalk-like appearance, hence the name "chalkbrood".<ref>{{cite journal |last1=James |first1=R.R. |last2=Skinner |first2=J.S. |title=PCR diagnostic methods for Ascosphaera infections in bees |journal=Journal of Invertebrate Pathology |date=October 2005 |volume=90 |issue=2 |pages=98–103 |doi=10.1016/j.jip.2005.08.004 |pmid=16214164 |bibcode=2005JInvP..90...98J }}</ref> Yeasts for small colonies [[in vitro]] and [[in vivo]], and excessive growth of ''[[Candida (genus)|Candida]]'' species in the mouth or vagina causes "thrush", a form of [[candidiasis]].

The cell walls of the ascomycetes almost always contain [[chitin]] and [[Beta-glucan|β-glucans]], and divisions within the hyphae, called "[[septum#In mycology|septa]]", are the internal boundaries of individual cells (or compartments). The cell wall and septa give stability and rigidity to the hyphae and may prevent loss of [[cytoplasm]] in case of local damage to cell wall and [[cell membrane]]. The septa commonly have a small opening in the center, which functions as a [[cytoplasm]]ic connection between adjacent cells, also sometimes allowing cell-to-cell movement of [[Cell nucleus|nuclei]] within a hypha. Vegetative hyphae of most ascomycetes contain only one nucleus per cell (''[[uninucleate]]'' hyphae), but [[multinucleate]] cells—especially in the apical regions of growing hyphae—can also be present.