藝術與建築詞典根目錄
....代理者層面
........活體有機體
............真核生物 (域)
................植物界 (界)
....................被子植物門 (門)
........................木蘭綱 (綱)
............................薔薇目 (目)
................................榆科 (科)
....................................榆屬 (屬)
|||........................................美國榆 (種)
|||........................................榔榆 (種)
|||........................................英國榆 (種)
|||........................................岩榆 (種)
|||........................................赤榆 (種)
|||........................................山榆 (種)