primordium

Leaf buttress A leaf primordium, appearing as a protuberance on the side of the stem apex, produced by periclinal division of the tunica and corpus, and associated with a procambium.

叶原座：顶端分生组织上的侧生突起发育成叶的原基，与原形成层有关。

The proter's oral primordium appears (under the pellical, too) anterior to the parent AZM2, from which membranells 7―11 of AZM1, the whole AZM2, PM and one of the frontal cirri will be originated;

（2）前仔虫口原基出现在老仔虫AZM2之前方深处，发育成前仔虫的AZM2、口侧膜及AZM1的一部分，并更新老结构AZM1中的第7―11片小膜。