Abstract
1. Mesocotyl and coleoptile length and mesocotyl-coleoptile elongation ratio (M-C ratio) in darkness were determined for 30 species of gramineous crops and grasses consisting of 22 genera and 4 subfamilies. 2. In common wheat, barley and rye, mesocotyl did not elongat, but coleoptile elongated up to 38-69 mm. 3. In the greater part of summer cereals and tropical grasses, the mesocotyl elongated up to 34-211 mm, whilc the coleoptile length was less than 10 mm. The M-C ratios of these crops and grasses varied from 6 to 36. 4. In rice, maize, oat and temperate grasses, both mesocotyl and coleoptile elongated; the M-C ratios of these crops and grasses were less than 5, and many of them were 2-3. 5. From the result of this investigation, gramineous crops and grasses were classified into 3 types (i.e., coleoptile elongation type, mesocotyle elongation type and intermediate type), based on the elongation of mesocotyl, coleoptile, and the M-C ratio. Wheat, barley and rye, which belong to the Triticeae of Festucoideae, showed the coleoptile elongation type. Panicoideae and Eragrostoideae showed the mesocotyl elongation type with the exception of maize. Oryzoideae and the Festuceae and Aveneae of Festucoideae showed the intermediate type, in which both mesocotyl and coleoptile elongate. 6. Mesocotyl length and the weight of 1000 seeds were positively and highly significantly correlated within the mesocotyl elongation type. 7. The M-C ratio of wild species was greater than that of cultivated species in the same genus.
