茎中有限外韧型维管束和油室数目不同，每种柴胡的维管束与油室数目相等，北柴胡为16个，南胡多为28～31个，少为16个。
The number of collateral vascular bundle and oil room are different , the North-Chaihu is 16 , The South-Chaihu is 28 to 31 , the least is 16 .
有限维管束