系2.四数花系——Ser. Sericeae (Crap.) Yu et Ku in Bull. Bot. Res. 1 (4): 2. 1981. ——Sect. Sericeae Crep. in Journ. Hort. Soc. Lond. 11: 226. 1889: Rehd. et Wils. in Sarg. Pl. Wls. 2:343. 1915.