What is the difference between the grains, between wheat and rye, or oat and barley?
A simple question. I thought. The answer seems not to be simple.
A farmer who sows wheat, knows that there is wheat on his field. That was on the packaging of the purchased seed. But if we are at a crossroads in four grain fields, can you see what kind of grain grows?

A search on the Internet yields many differences: in yield, fertilizer use, protein content, composition, minerals and suitable land.
Plant Guides and fauna give some botanical differences.
Contacted agricultural engineers and university professors stick to
- A (too?) complex case,
- Differences are not always clear,
- The potential for confusion by winter, summer and intermediate species,
- Unclear by many crosses and hybrids, varieties and species.

And here I am as a layman in the field, and still do not know what grain there grows under my nose.
The attempt to bring some light into the darkness becomes a challenge.

The advent of agriculture evolves along with the cultivation of cereals: einkorn in the Middle East and Europe, in Asia rice, maize in America and millet in Africa.
By a spontaneous cross between two diploid wild wheat species (with 14 chromosomes) originated fertile emmer wheat (tetraploid with 28 chromosomes).

Domesticated emmer first emerged at Tell Aswad, Syria around 9,220 to 9,000 BC.
Wild einkorn (Triticum monococcum subsp. Boeoticum) would be around 9,000 BC. evolve into einkorn (Triticum monococcum subsp. monococcum).
Wild goatgrass (Aegilopsis speltoides) crossed with Urartu wheat (Triticum Urartu) to wild emmer (Triticum turgidum subsp. Dicoccoides) that has been domesticated for emmer (Triticum turgidum subsp. Dicoccum). This evolved into macaroni wheat (Triticum turgidum subsp. Durum). This, again crossed with wild goatgrass yielded around 6,000 BC. spelt (Triticum aestivum subsp. spelta) and evolved to bread wheat (Triticum aaestivum subsp. vulgare).

Thanks to the large seeds with many reserves they have a rapid growth and overshadow other crops.

Domesticated plants for reproduction need humans (crosses, sowing, harvesting, distribution). Properties to survive in the wild were lost. And by the way of sowing, harvesting and storage were retained other characteristics.

Hans Vermeulen has composed for Natuurpunt a course ”On old and new cereals”. The best and most extensive that I could find in this area. I largely based me on this to distinct (with the naked eye) features at a glance and put them in a schedule. Because his work looks very solid to me, I have, if I saw conflicting information (e.g. number of grain per husk) based on his information.

In order to distinguish the cereal crop it is necessary to know the characteristic parts of the plant.

Cereals is the collective name for the fruit of monocot crops from the family of grasses (Gramineae or Poaceae).

The leafs are like grass with long, narrow and parallel veins. In the length of the leaf are often ribs.
The leaf begins on a thickening of the stem (or culm): the node. The lower part of the sheet forms a sleeve around the stem, the leaf sheath. Above this enclosure is less dense, at the edges of the sheath can be formed a film.
The second part, the lamina, is separate from the stem. (When the top sheet of the stem, this is called the flag leaf.) At the transition of leaf sheath to leaf blade you often see a ring of hairs or a film, the tongue or ligule. A collar or protruding ears (auricles) are possible here.

Typically part of the inflorescence of grasses are the spikelets.
A spikelet may have one or more flowers (with pistil, stamen and (corn) fruits).
The lower (outer) two leaves of a spikelet are called (outer) glumes. They can completely enclose a spikelet. If not so, are the successive leaves of the spikelet imbricated. A sharp keel shape we call keeled.
Then follow two scales, the husk.
The first (bottom) husk at the axis (rachilla) of the spikelet is the lemma, thin and crispy.
The following is the palea, often membranous and limp.
At the top of the lemma, many grasses have a long whip, the continuous midrib or awn.
The spikelets are by 1 to 3 on teeth to the extension of the grass stalk, the unbranched rachilla. Spikelets often sit in two rows along the rachilla.

Grains can grow in spikes (wheat, rye and barley), panicles (millet and oats), cobs (maize). (Or fruits: buckwheat grain, is actually not a grain).

When ripe, the heavy spike of wheat bends the base, the stem, but not the spike itself. In barley, the spike does make a curve. When barley is the fruit fused with the surrounding husks.

Given so many different types of grains exist, it is impossible to pour all of them in one table. I limit myself to the most common here.

To keep it clear, and because my knowledge of websites and tables is insufficient to present them organized, I split them into wheat and related, and wheat versus other types.

Wheat table

Cereals table

Improvements, additions or proper identification flowchart are very welcome!