Thellung 1918 [reference] revised the species concept of Triticum sensu stricto by constructing the genus with only three species, each a domesticated species under which the other wild and domesticated taxa are ranked as subspecies. Thellung's revision was introduced into the modern taxonomy of MacKey (1966, 1988) who followed Thellung's species concept to structure his genetically based Triticum classification. The Thellung classification is presented here in its original form with corrections in spelling and authority citations.
| 1. Triticum monococcum L. | |
| I. subsp. aegilopoides (Link) Thell. | |
| II. subsp. cereale Asch. & Graebner | [= 'monococcum'] |
| 2. Triticum turgidum L. | |
| I. subsp. dicoccoides (Körn. ex Asch. & Graebner) Thell. | |
| II. subsp. dicoccum (Schrank ex Schübler) Thell. | |
| III. subsp sementivum (Flaksb.) Thell. | [= 'durum'] |
| subsp. turgidum | |
| IV. subsp. polonicum (L.) Thell. | |
| 3. Triticum aestivum L. | |
| I. subsp. spelta (L.) Thell. | |
| II. subsp. aestivum | |
| subsp. compactum (L.) Thell. |