子叶节区上部的管状中柱和④上胚轴－苗端的真中柱。
The type of siphonostele in the upper part of cotyledon node zone and the type of eustele in epicotyl - shoot zone .
一种管状中柱，其中初生脉管组织排列在髓孔周围，存在于大多数种子植物中。
The central cylinder in which the primary vascular tissue is arranged around a pith , as in most seed plants .
管状中柱管状中柱管状中柱