Pollen identification is a reading of characters, not a lookup. A grain has a size, a shape, a polarity, a number and kind of aperture, and a surface sculpture, and those five readings together narrow the field. The resources below are grouped by the question you are actually asking at the microscope, because that is the order the work happens in: describe what you see, compare it against reference material, then resolve the name against a nomenclatural authority.
Light microscopy usually supports family or genus, not species. The grasses are the standard illustration: Poaceae pollen is uniform enough that most of it cannot be separated below family, though a few cereals — rye and maize among them — have grains distinctive enough that a species name is defensible. That pattern is general. Palynologists classify conservatively because the morphological differences between related species are often too small to describe reliably, and a confident species name from a single grain is the most common way a pollen record becomes untrustworthy. It is also worth keeping the two ideas separate: a pollen type is a morphological category, and a plant taxon is a taxonomic one. Recording the characters you measured — and naming the ones you could not resolve — is worth more than a determination the evidence cannot carry.
Before you reach for an atlas
Record the characters first.
Matching a photograph against a memory is how misidentifications happen. Working through
these in order gives you a description that someone else can check — and that stays
useful even if the determination later changes.
Size
Measure the longest axis in micrometres, and say how the grain was prepared.
Preparation changes dimensions substantially. Acetolysed, hydrated and dry grains of the same taxon do not measure the same, so a size without a stated preparation is not comparable to a published figure. Record the objective, numerical aperture and how the scale was calibrated alongside the measurement.
Shape
Record the ratio of the polar axis to the equatorial diameter (P/E).
The P/E ratio places a grain on Erdtman's series: oblate below 0.75, spheroidal around 0.88–1.14, prolate from 1.33 to 2.00, with peroblate and perprolate at the extremes. It can only be read when you know which view you are in, so shape and polarity are read together rather than separately.
Polarity and symmetry
State whether you are looking at the grain in polar or equatorial view.
Note whether the grain is isopolar or heteropolar, and whether it is radially or bilaterally symmetric. Getting this wrong inverts the aperture reading, which is the single most consequential error in a description.
Apertures
Count the apertures and describe their kind and position.
This is the highest-information character. Distinguish elongate furrows (colpi) from rounded pores (pori) and from grains carrying both (colporate). A single distal furrow (sulcate) is common in monocots; some taxa are inaperturate. Record the number, the position, and whether you could resolve the type at all.
Surface sculpture
Describe the ornamentation of the outer wall.
Psilate, scabrate, echinate, reticulate, striate, verrucate, gemmate, clavate, baculate, foveolate and rugulate are the common classes. Much of the standard terminology turns on a one-micrometre threshold — scabrate elements fall below it, echinate spines and reticulate lumina above it — so the distinction is a measurement rather than an impression. Sculpture is also where light microscopy most often reaches its limit: ornamentation that separates two genera may be resolvable only with SEM, and saying so is part of the description.
Wall structure
Note the exine stratification if your optics can resolve it.
Whether a grain is tectate, semitectate or intectate — and whether columellae are visible — usually requires careful focusing through the grain. If your setup cannot resolve it, record that as unresolved rather than omitting the character silently.
These are the observations. Standards covers the vocabularies
that carry them into a record — including Darwin Core for biological occurrences,
REMBI and OME for imaging, and ABCD-EFG for geological material — while each observation
profile records its own method-specific context. Prepare a
contribution covers what to keep alongside the files themselves.
Resources
Grouped by the question you are asking.
A resource can appear under more than one heading. Each entry states who maintains it,
what it is best for, and where it stops being reliable.
Nothing here matches that.
Clear the filter, or search the whole library from the library index.
Describe what you observed
Character guides and controlled terminology, so your description means the same thing to the next reader.
Division of Structural and Functional Botany, University of Vienna, supervised by AutPal
A palynological database in which an entry ideally carries a detailed grain description, LM, SEM and TEM images, images of the plant and flower, and the relevant literature.
Best for
Checking a description against a carefully written one for the same taxon, and seeing the same grain across several imaging modalities at once.
Limits
Coverage is entry-by-entry rather than comprehensive — roughly 4,650 species at last check — and not every taxon carries the full complement of description, images and literature. The electron-microscope images show detail you will not resolve on a light microscope, which makes them easy to over-read when matching your own view.
Coverage
Global, with strong European representation. Modern pollen and spores; roughly 4,650 species across 1,810 genera.
Reuse
Custom licence, not Creative Commons: educational and non-commercial use only, with the photographer and PalDat credited. Commercial use requires written permission.
Imaging
Light microscopy · Light microscopy, hydrated · Scanning electron microscopy · Transmission electron microscopy
Contributing
Free online access to read; a free registration is required to publish data.
In 2021 PalDat absorbed the PONET database, adding more than 2,000 datasets of high-resolution light micrographs of hydrated pollen. That hydrated-LM material is the closest published analogue to what you are actually seeing down the tube, and it is the part of PalDat to reach for first if you are matching against your own light-microscope view.
Halbritter et al., Illustrated Pollen Terminology, 2nd edition (2018)
Halbritter, Ulrich, Grímsson, Weber, Zetter, Hesse, Buchner, Svojtka & Frosch-Radivo; published by Springer
A book-length illustrated treatment of pollen terminology, pairing each term with photographs of real grains showing the feature.
Best for
Learning what a term actually looks like down the tube, rather than what its definition says.
Limits
A terminology reference, not an identification key — it will teach you to describe a grain precisely but will not tell you which taxon it belongs to. Many illustrations are electron micrographs showing detail a light microscope cannot resolve.
Coverage
Global; over 300 terms with more than a thousand images.
Reuse
Not stated by the maintainer.
Imaging
Light microscopy · Scanning electron microscopy · Transmission electron microscopy
Published under a CC BY 4.0 licence, so the full book is legitimately free to download and redistribute — unusual for a reference of this standing, and the single best starting point if you are buying nothing. Its terminology is also browsable through PalDat.
Review of Palaeobotany and Palynology (Elsevier); prepared by the IFPS working group on palynological terminology
The community's standard glossary, defining roughly two thousand terms and attributing each to the author who introduced it.
Best for
Settling exactly what a term means, and which author's sense of it a source is using, when two references appear to disagree.
Limits
Paywalled on the publisher's site, and it is text rather than an illustrated guide — it defines terms precisely but shows you very little. Copies circulating on university teaching pages are not an official open-access release, so do not rely on one being there.
Coverage
Global; pollen and spore morphology terminology.
Reuse
Not stated by the maintainer.
There is no formal TDWG or machine-readable ontology for pollen morphology. This glossary is the de facto standard by community convention, which is worth knowing if you are trying to map a description onto structured fields.
Glossary Subscription Research pass ·
Compare against reference evidence
Atlases, catalogues and reference collections for comparing an unknown with documented material or measurements.
Division of Structural and Functional Botany, University of Vienna, supervised by AutPal
A palynological database in which an entry ideally carries a detailed grain description, LM, SEM and TEM images, images of the plant and flower, and the relevant literature.
Best for
Checking a description against a carefully written one for the same taxon, and seeing the same grain across several imaging modalities at once.
Limits
Coverage is entry-by-entry rather than comprehensive — roughly 4,650 species at last check — and not every taxon carries the full complement of description, images and literature. The electron-microscope images show detail you will not resolve on a light microscope, which makes them easy to over-read when matching your own view.
Coverage
Global, with strong European representation. Modern pollen and spores; roughly 4,650 species across 1,810 genera.
Reuse
Custom licence, not Creative Commons: educational and non-commercial use only, with the photographer and PalDat credited. Commercial use requires written permission.
Imaging
Light microscopy · Light microscopy, hydrated · Scanning electron microscopy · Transmission electron microscopy
Contributing
Free online access to read; a free registration is required to publish data.
In 2021 PalDat absorbed the PONET database, adding more than 2,000 datasets of high-resolution light micrographs of hydrated pollen. That hydrated-LM material is the closest published analogue to what you are actually seeing down the tube, and it is the part of PalDat to reach for first if you are matching against your own light-microscope view.
Division of Structural and Functional Botany, University of Vienna
PalDat's own curated set of links to other palynology sites, collections and projects.
Best for
Finding the regional atlas or specialist collection that no general list will have thought to include.
Limits
A link list maintained by a third party, with no stated review cadence. Expect dead links: at the last check it still listed the University of Arizona's pollen image catalogue, which returns a 404. Treat it as a set of leads to verify, not a vetted index.
Coverage
Global, weighted toward European institutions.
Reuse
Not stated by the maintainer.
Worth mining rather than duplicating. If you are looking for something this library does not yet list, start here before searching generally.
PalaeoWorks Laboratory, Department of Archaeology & Natural History, The Australian National University
Free online access to the largest pollen and spore collection in the Australasian region, with details on over 15,000 species, searchable or browsable by family.
Best for
Australasian material, where a European or North American atlas will simply not contain the taxon you are looking at.
Limits
Regional by design, and of limited use outside Australasia. The 15,000-species figure counts records with morphological and locality metadata — image coverage is considerably thinner, and it is normal to reach a fully described record that carries no photograph at all. Light microscopy only.
Coverage
Australasia. Over 15,000 species described. The physical collection is held at ANU in Canberra.
Reuse
CC BY-NC-SA 3.0, stated site-wide.
Imaging
Light microscopy
The site is explicitly built for amateurs as well as professionals, which makes it an unusually good starting point. For contributors working on Australian material this is the first place to look, not the last.
Oxford Long-Term Ecology Laboratory, University of Oxford; funded by the UK Natural Environment Research Council
An open platform serving two purposes: identifying unknown grains, and acting as a morphological reference collection.
Best for
Focusing through a grain the way you would at the microscope, rather than reading a single fixed-focus photograph.
Limits
Coverage depends on what the community has contributed, so it is uneven across taxa and regions, and it is light microscopy only — no electron micrographs. A crowd-sourced determination is evidence about a grain, not an authority on it. Development also appears to have slowed: at the last check some linked occurrence feeds had not refreshed since 2022, one headline counter on the front page read zero, and the public API is still labelled a preview.
Coverage
Global, community-contributed. Roughly 2,340 species across 2,771 digitised slides at last check.
Reuse
CC BY 4.0 for the Global Pollen Project reference dataset, as stated in its terms.
Imaging
Light microscopy
Contributing
Unknown grains can be uploaded for crowd-sourced identification, mediated by an identification model; once they satisfy it they pass into the master reference collection.
Grains are presented as five-image z-stacks you can focus through, emulating a light microscope. That makes it the closest thing available to comparing your own view against a reference, rather than comparing your view against a photograph of one.
Beug, Leitfaden der Pollenbestimmung für Mitteleuropa und angrenzende Gebiete
Verlag Dr. Friedrich Pfeil, Munich
The standard identification key for Central European pollen, with keys, plates and comparative tables.
Best for
Working systematically to a determination on Central European material, rather than browsing images and hoping for a match.
Limits
German-language only, and regionally scoped to Central Europe and adjacent areas — of limited use elsewhere. In print and priced accordingly rather than free.
Coverage
Central Europe and adjacent regions. 542 pages, 120 plates.
Reuse
Not stated by the maintainer.
A worked key is a different tool from an image atlas: it forces you through the characters in order, which is exactly the discipline that stops a determination resting on one striking feature.
Identification key Print Research pass ·
Resolve the name or identifier
Authorities that settle an accepted biological or mineral name, astronomical designation or other stable identifier.
The international occurrence infrastructure and taxonomic backbone against which biodiversity records are commonly resolved.
Best for
Checking that the plant name your determination lands on is current, and seeing where the taxon has actually been recorded.
Limits
Not pollen-specific, and the backbone is an aggregation rather than a nomenclatural authority in its own right — for contested names, check a botanical authority as well. Occurrence coverage reflects collection effort, not true distribution.
Coverage
Global, all taxa.
Reuse
Not stated by the maintainer.
Not pollen-specific, but it is the occurrence backbone the Global Pollen Project links against and a useful example of Darwin Core data in practice. Clio has no GBIF publishing connection.
Beug, Leitfaden der Pollenbestimmung für Mitteleuropa und angrenzende Gebiete
Verlag Dr. Friedrich Pfeil, Munich
The standard identification key for Central European pollen, with keys, plates and comparative tables.
Best for
Working systematically to a determination on Central European material, rather than browsing images and hoping for a match.
Limits
German-language only, and regionally scoped to Central Europe and adjacent areas — of limited use elsewhere. In print and priced accordingly rather than free.
Coverage
Central Europe and adjacent regions. 542 pages, 120 plates.
Reuse
Not stated by the maintainer.
A worked key is a different tool from an image atlas: it forces you through the characters in order, which is exactly the discipline that stops a determination resting on one striking feature.
Kew's published taxonomy, synonymy, distribution and descriptions for the world's vascular plants, built on the World Checklist of Vascular Plants.
Best for
Checking whether the plant name your determination landed on is currently accepted, and what it is a synonym of if not.
Limits
Depth and currency still vary by plant group, and the taxonomy reflects Kew's editorial judgement rather than a multi-institution consensus — for a contested name, compare against World Flora Online. There is no documented public API.
Coverage
Global; vascular plants. Names and distributions refreshed weekly.
The World Flora Online Consortium — founded by Missouri Botanical Garden, New York Botanical Garden, Royal Botanic Garden Edinburgh and Royal Botanic Gardens Kew, now 50-plus institutions
An open, multi-institution consensus taxonomy for all known plants, published as a continuously curated backbone with citable twice-yearly snapshots.
Best for
A name check that reflects agreement across institutions rather than one herbarium's position, and a versioned snapshot you can cite.
Limits
Taxonomic depth depends on whether an active expert network covers the family in question; groups without one may still reflect the 2013 Plant List baseline it was seeded from.
Coverage
Global; all known plants. Citable snapshots cut on 21 June and 21 December each year.
Reuse
Portal content CC BY 4.0; the downloadable taxonomic backbone is released CC0 1.0.
This supersedes The Plant List, which is now offline entirely. If a guide or paper points you at theplantlist.org, it is out of date.
Atlas of Living Australia — hosted by CSIRO, supported by NCRIS, and the Australian node of GBIF
Australia's national biodiversity platform: occurrence records, species profiles and imagery, with name matching against the Australian Plant Census.
Best for
Confirming that a plant you have determined actually occurs where you found it, and resolving Australian plant names against the national authority.
Limits
Australian in scope and in taxonomy — plant names resolve against the Australian Plant Census, so names outside an Australian context are handled less authoritatively here than in POWO or World Flora Online. Occurrence coverage reflects collecting effort, not true distribution.
Coverage
Australia; over 100 million occurrence records across thousands of datasets.
Reuse
CC BY 3.0 Australia.
Paired with APSA, this is the practical Australian workflow: match the grain against the regional atlas, then check the resulting name and its distribution here.
Data repository Open API Research pass ·
Use the right method
Published field, preparation, imaging, measurement and analysis methods, with their limitations and safety requirements.
A published laboratory protocol for extracting pollen from sediment, covering reagents, sequence and the safety regime each step requires.
Best for
Understanding what a full preparation actually involves before deciding whether to attempt it or send the sample to a laboratory.
Limits
Written for a staffed university laboratory operating under UK COSHH requirements. It assumes a fume hood, institutional training and supervision, and it is not adaptable to a home setting — several steps involve hydrofluoric acid.
Coverage
Sediment-based pollen extraction.
Reuse
Not stated by the maintainer.
Read the safety section on this page before the method section. It is unusually explicit about the hazards, including the buddy system and calcium gluconate requirements for hydrofluoric acid work.
Originally Munksgaard, later Blackwell and John Wiley & Sons; scanned copy hosted by the Internet Archive
The long-standing standard textbook of pollen analysis, covering laboratory technique alongside the morphological system used to describe grains.
Best for
Building the underlying method properly, rather than assembling it from separate protocols and glossaries.
Limits
The linked scan is the 1975 third edition and is borrow-only under controlled digital lending, not a free download; the 1989 fourth edition is the one usually cited and is available only in print. Laboratory safety practice has moved on considerably since either, so do not take its procedures as current guidance.
Coverage
General method; Northern European emphasis in its examples.
Reuse
Not stated by the maintainer.
Contributing
A free Internet Archive account is required to borrow the scanned copy.
Textbook Free registration Research pass ·
Place it in context
Occurrence, stratigraphic, catalogue and archive services that situate a record in space, time and literature.
An international, community-governed consortium of data stewards, funded by the US National Science Foundation
A community-curated database covering fossil pollen among many other palaeoecological proxies, reachable through a map interface, an API, an R package and DOIs.
Best for
Placing a fossil pollen record in its stratigraphic and regional context, and seeing how comparable assemblages have been reported.
Limits
Palaeoecological rather than identification-focused — it will not help you name a grain. Coverage reflects where researchers have worked, which is heavily weighted toward North America and Europe.
Coverage
Global, unevenly. Fossil and sub-fossil material across many proxies.
Reuse
CC BY 4.0, stated in its data use and embargo policy.
Relevant to Clio less for identification than as a precedent: it is a working example of versioned, citable, community-curated records, which is the model Clio is building toward.
The international occurrence infrastructure and taxonomic backbone against which biodiversity records are commonly resolved.
Best for
Checking that the plant name your determination lands on is current, and seeing where the taxon has actually been recorded.
Limits
Not pollen-specific, and the backbone is an aggregation rather than a nomenclatural authority in its own right — for contested names, check a botanical authority as well. Occurrence coverage reflects collection effort, not true distribution.
Coverage
Global, all taxa.
Reuse
Not stated by the maintainer.
Not pollen-specific, but it is the occurrence backbone the Global Pollen Project links against and a useful example of Darwin Core data in practice. Clio has no GBIF publishing connection.
Atlas of Living Australia — hosted by CSIRO, supported by NCRIS, and the Australian node of GBIF
Australia's national biodiversity platform: occurrence records, species profiles and imagery, with name matching against the Australian Plant Census.
Best for
Confirming that a plant you have determined actually occurs where you found it, and resolving Australian plant names against the national authority.
Limits
Australian in scope and in taxonomy — plant names resolve against the Australian Plant Census, so names outside an Australian context are handled less authoritatively here than in POWO or World Flora Online. Occurrence coverage reflects collecting effort, not true distribution.
Coverage
Australia; over 100 million occurrence records across thousands of datasets.
Reuse
CC BY 3.0 Australia.
Paired with APSA, this is the practical Australian workflow: match the grain against the regional atlas, then check the resulting name and its distribution here.
Data repository Open API Research pass ·
Learn the field
Textbooks, courses and teaching material for building the underlying competence.
Division of Structural and Functional Botany, University of Vienna
PalDat's own curated set of links to other palynology sites, collections and projects.
Best for
Finding the regional atlas or specialist collection that no general list will have thought to include.
Limits
A link list maintained by a third party, with no stated review cadence. Expect dead links: at the last check it still listed the University of Arizona's pollen image catalogue, which returns a 404. Treat it as a set of leads to verify, not a vetted index.
Coverage
Global, weighted toward European institutions.
Reuse
Not stated by the maintainer.
Worth mining rather than duplicating. If you are looking for something this library does not yet list, start here before searching generally.
Halbritter et al., Illustrated Pollen Terminology, 2nd edition (2018)
Halbritter, Ulrich, Grímsson, Weber, Zetter, Hesse, Buchner, Svojtka & Frosch-Radivo; published by Springer
A book-length illustrated treatment of pollen terminology, pairing each term with photographs of real grains showing the feature.
Best for
Learning what a term actually looks like down the tube, rather than what its definition says.
Limits
A terminology reference, not an identification key — it will teach you to describe a grain precisely but will not tell you which taxon it belongs to. Many illustrations are electron micrographs showing detail a light microscope cannot resolve.
Coverage
Global; over 300 terms with more than a thousand images.
Reuse
Not stated by the maintainer.
Imaging
Light microscopy · Scanning electron microscopy · Transmission electron microscopy
Published under a CC BY 4.0 licence, so the full book is legitimately free to download and redistribute — unusual for a reference of this standing, and the single best starting point if you are buying nothing. Its terminology is also browsable through PalDat.
Originally Munksgaard, later Blackwell and John Wiley & Sons; scanned copy hosted by the Internet Archive
The long-standing standard textbook of pollen analysis, covering laboratory technique alongside the morphological system used to describe grains.
Best for
Building the underlying method properly, rather than assembling it from separate protocols and glossaries.
Limits
The linked scan is the 1975 third edition and is borrow-only under controlled digital lending, not a free download; the 1989 fourth edition is the one usually cited and is available only in print. Laboratory safety practice has moved on considerably since either, so do not take its procedures as current guidance.
Coverage
General method; Northern European emphasis in its examples.
Reuse
Not stated by the maintainer.
Contributing
A free Internet Archive account is required to borrow the scanned copy.
Erdtman (1943), An Introduction to Pollen Analysis
Chronica Botanica; scanned copy hosted by the Internet Archive
Erdtman's introductory text, the source of much of the shape and aperture vocabulary still in use.
Best for
Seeing where the descriptive system came from, and why it is built the way it is.
Limits
Published in 1943. Its taxonomy, distribution data and laboratory safety practice are all long out of date, and it should be read for the origin of the concepts rather than as current guidance.
Coverage
General introduction; historical.
Reuse
Not stated by the maintainer.
Freely downloadable in full, unlike most of the classic literature. Useful background, not a working reference.
Mander & Punyasena (2014), International Journal of Plant Sciences 175(8)
International Journal of Plant Sciences, University of Chicago Press
A review of why pollen and spore records characteristically describe plant life at a rank above species, and what drives that limit.
Best for
Understanding why the determination ceiling exists rather than taking it on trust — and having something citable when you record a family-level identification.
Limits
Paywalled, and it is an analysis of the problem rather than a guide to working around it. It will not help you identify a grain.
Coverage
General; palynological taxonomic resolution.
Reuse
Not stated by the maintainer.
The paper attributes conservative genus- and family-level classification to the difficulty of describing very small morphological differences between species with the available terminology. That is the honest reason a species name is usually not on offer.
Journal Subscription Research pass ·
Safety
Some observations and preparations need specialist safeguards.
Hazards change with the field, site, material and equipment. Follow the requirements of
the source method, manufacturer, facility and relevant authority, and do not improvise
a procedure whose controls or training you do not have.
Acetolysis is a fume-hood procedure and needs training
Erdtman's acetolysis, the standard preparation for making exine features visible, uses roughly nine parts acetic anhydride to one part concentrated sulfuric acid, heated. The mixture is corrosive and strongly exothermic, and it reacts violently with water — published protocols insist that all glassware, tips and reagents be scrupulously dry for exactly that reason. It requires a fume hood, appropriate personal protective equipment, supervised training, and a proper route for chemical waste. No page can substitute for the safety instruction your institution requires.
Hydrofluoric acid requires a specialist facility, not care
Where sediment samples need silicates removed, protocols call for hydrofluoric acid. HF is not simply a stronger acid: it penetrates skin without necessarily causing immediate pain, continues destroying soft tissue and bone for hours, and can cause fatal systemic effects by stripping calcium from the body after an exposure that looked minor. Institutional protocols require a laboratory equipped for it, trained personnel, a buddy system, and calcium gluconate on site, with medical follow-up after any contact. A death from dermal HF exposure in a palynology laboratory is documented in the occupational-health literature (Muriale et al., 1996). If a protocol calls for HF, the safe response is to route the sample to an equipped laboratory.
Much useful work needs no hazardous chemistry at all
Fresh pollen mounted in glycerine jelly or water, under a good light microscope, supports a great deal of legitimate description — and hydrated material is closer to published hydrated-LM reference images than an acetolysed preparation is. It is worth knowing what acetolysis actually does: it works by destroying everything that is not the resistant exine, including the intine, so it is a trade of information for contrast rather than a straightforward improvement. If you are starting out, start with hydrated material.
This is orientation, not laboratory training, and it is not a substitute for the safety
instruction and supervision your institution requires.
Corrections
Know this field better than this page does?
The most valuable correction is not another link. It is knowing that an entry's stated limit
is wrong, or that a resource practitioners rely on is missing.
