ConidiaAsexual spores made in chains. One of them is a conidium.
PhialidesFlask-shaped cells that make the conidia, one after another.
VesicleThe swollen tip of the conidiophore. The phialides stand on it.
ConidiophoreThe stalk that carries the spores. It is a special hypha.
Foot cellThe cell of the hypha that the conidiophore grows from.
Septate hyphaA thread of the mold, divided into cells by cross walls.
SeptumA hypha's cross wall.
Penicillium 3
MetulaeShort cells that carry the phialides. One of them is a metula.
BranchA cell that links stipe and metulae. Some kinds have none.
StipeThe stalk of the conidiophore. The brush sits on top of it.
How this list was compiled: Every name checked on 2026-10-03 and kept only where two of these use it. (1) University of Adelaide, Mycology Online: Aspergillus, Penicillium, and Glossary of Mycological Terms, https://mycology.adelaide.edu.au/fungal-descriptions-and-antifungal-susceptibility/hyphomycetes-conidial-moulds/aspergillus , https://mycology.adelaide.edu.au/fungal-descriptions-and-antifungal-susceptibility/hyphomycetes-conidial-moulds/penicillium , https://mycology.adelaide.edu.au/glossary (read for the names of structures only): Aspergillus conidiophores terminate in a vesicle covered with phialides in one layer (uniseriate) or with metulae which bear small whorls of phialides (biseriate); the conidial head: vesicle, phialides, any metulae and conidia; conidia have one cell and are produced in long dry chains; conidiophore stipes; foot cell, the basal cell of an Aspergillus conidiophore; in Penicillium a phialide makes chains of one-celled conidia in basipetal order, the youngest conidium at the base of the chain; phialides singly, in groups or from branched metulae give a brush-like appearance (a penicillus); metulae are the last branches before the phialides and bear a whorl of them; every cell between metulae and stipe is called a branch; phialides are usually flask-shaped; conidiophore, a special hypha on which conidia grow; conidium, an asexual reproductive propagule; septum, a cross wall in a hypha; sporangiospore, an asexual spore made inside a sporangium. (2) Wikipedia, Conidium, Phialide, Glossary of mycology, Hypha, Aspergillus flavus, Penicillium, Penicillium expansum, Rhizopus stolonifer, https://en.wikipedia.org/wiki/Conidium , https://en.wikipedia.org/wiki/Phialide , https://en.wikipedia.org/wiki/Glossary_of_mycology , https://en.wikipedia.org/wiki/Hypha , https://en.wikipedia.org/wiki/Aspergillus_flavus , https://en.wikipedia.org/wiki/Penicillium , https://en.wikipedia.org/wiki/Penicillium_expansum , https://en.wikipedia.org/wiki/Rhizopus_stolonifer : a conidium is a fungal spore, asexual and non-motile, produced exogenously and borne on specialized stalks called conidiophores; the phialide is a flask-shaped outgrowth of the vesicle (the dilated top of the conidiophore), a bottle-shaped cell that makes conidia in basipetal order and grows no longer; vesicle, the swollen apex of the conidiophore of Aspergillus; foot cell, a hyphal cell that supports the conidiophore in Aspergillus; uniseriate and biseriate, where phialides rest on sterile cells called metulae; penicillus, a brush-shaped conidial head, characteristic of Penicillium stipes; hyphae are divided into cells by cross-walls called septa; the hyphae of Aspergillus flavus are septate; the brush-like conidiophore of Penicillium, with branch points below the phialides; a sporangiospore is a spore produced within a sporangium, a sac-like structure; black bread mold has unbranched sporangiophores and black sporangia. (3) P. Krijgsheld and others, Development in Aspergillus, Studies in Mycology 74, 2013 (Utrecht University), https://pmc.ncbi.nlm.nih.gov/articles/PMC3563288/ : the conidiophore stalk is formed from a specialized foot cell within the mycelium; the tip of the stalk swells and forms a vesicle; in biseriate species the vesicle bears metulae and on them phialides, in uniseriate species the phialides sit directly on the vesicle; the phialides give rise to chains of conidia; the septa of the hyphae are porous. (4) C. M. Visagie and others, Identification and nomenclature of the genus Penicillium, Studies in Mycology 78, 2014, https://pmc.ncbi.nlm.nih.gov/articles/PMC4261876/ : biverticillate conidiophores carry a whorl of three or more metulae from the stipe's end to the phialides; terverticillate conidiophores branch once more, from stipe to metulae, a continuation of the stipe and one side branch or a whorl of three or more branches. (5) C. S. Gager, Fundamentals of Botany, 1916 (public domain), sections 253 and 260, https://archive.org/details/fundamentalsofbo00gagerich : in bread mold a globular sporangium develops at the tip of each upright hypha, the sporangiophore; in a mildew, short branches (conidiophores) each bear a chain of spores (conidia). Licence: own work
The drawing: Drawn for this site on 2026-10-03 from plain geometry; own work, nothing traced. Licence: own work
How it works
This conidia spore cell diagram shows where conidia form. They are asexual spores. In the two molds drawn here, Aspergillus and Penicillium, they form in chains on flask-shaped cells called phialides.
Read the full guide
The Aspergillus head
A conidiophore rises from a foot cell of the hypha and swells into a vesicle. Phialides cover the vesicle, and each one makes a chain of conidia. Together they are the conidial head.
The Penicillium brush
The stalk, or stipe, forks into branches. Each branch carries metulae, and each metula carries a whorl of phialides. The whole brush is called a penicillus.
In some kinds of Aspergillus the phialides sit on metulae too. Such a head is called biseriate.
Bread mold makes its spores inside a round case, the sporangium. Conidia form in the open.
A phialide makes conidia one after another, so the youngest conidium is at the base of its chain.
Questions and answers
What are conidia?
Conidia are asexual spores of a fungus. They form on special hyphae called conidiophores. One of them is a conidium.
What is the difference between conidia and sporangiospores?
Both are asexual spores. Conidia form in the open, on a conidiophore. Sporangiospores form inside a sac called a sporangium, as in bread mold.
What is a phialide?
A flask-shaped cell that makes conidia one after another, in a chain, without growing longer itself. Aspergillus and Penicillium both bear their conidia on phialides.
How do Aspergillus and Penicillium differ under a microscope?
An Aspergillus conidiophore starts from a foot cell and ends in a swollen vesicle covered with phialides. A Penicillium conidiophore branches into metulae and phialides, like a brush.