关键词: 禾本科植物, 幼苗, 进化

Abstract: According to basic characters and basic types of grass seedlings, evolutionaryrelationships of grass groups are studied in'this paper. The ancestral grass seedlingmorphological shapes were: the first leaf broad and short, the mesocotyl elongative, the mesocotyl roots absent, the sculletum and coleorhiza node roots absent, thecoleoptile node roots a few or absent. The modern seedling types of each subfamilytvers directly or indirectly evoluted frpm ancestral grass seedlings. Evolutionarytrends were from broad and short to narrow and long for the first leaf, fromlacking to appearing and increasing for the mesocotyl roots. the coleoptile noderoots and the sculletum and coleorhiza node roots. The evolutionary order anddistribution of the grass seedling types between and within subfamilies showed thegradual spread, migration and adaption of every grass groups from their originalplace to their distributive place.

Key words: Grasses, Seedling, Evolution