primordium

1.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：顶端分生组织上生突起叶原基，与原形层有关。

2.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，其随后前仔虫AZM2、口膜及AZM1一部分，并更新老结构AZM1中第7―11片小膜。