Floral development of Dichocarpum , Thalictrum , and Aquilegia (Thalictroideae, Ranunculaceae)

We examined the floral development of Dichocarpum fargesii , Thalictrum fargesii, Thalictrum przewalskii , and Aquilegia yabeana in Thalictroideae, Ranunculaceae, by scanning electron microscope. The sepals are initiated spirally in D. fargesii and A. yabeana , and in two pairs (with four sepals) or spirally (with five sepals) in T. fargesii and T. przewalskii . The petals in D. fargesii and A. yabeana and the stamens and carpels are initiated in a whorled pattern in all three genera. The floral phyllotaxis is whorled in these genera. The primordia of sepals are lunular and truncate, but that of petals and/or stamens are hemispherical, rounded, and much smaller than the sepal primordia. A relatively long plastochron exists between the last sepal and the first petal in D. fargesii and A. yabeana or the first stamen in T. fargesii and T . przewalskii . The similarity between the primordia of petals and stamens may indicate an evolutionary relationship between petals and stamens. The petals develop slower than the stamens in D. fargesii , but faster than stamens in A. yabeana . The early developmental stages of the staminodes in A. yabeana are similar to that of stamens, so they may be phylogenetically homologous organs. The carpel primordia are initiated in a single whorl; are lunular in shape and plicate in A. yabeana and D. fargesii ; and are initiated spirally and hemispheric in shape and ascidiate in T. fargesii and T. przewlaskii . The stigma is everted and decurrent with unicellular papillae in T. fargesii and T. przewalskii ; the head has unicellular papillae in D. fargesii and is smooth in A. yabeana . The floral development features of Aquilegia are unique in Thalictroideae.