由上皮及间叶两个胚叶构成，状似胚胎肺。
Histologically they looked like the embryonic lung consisted of epithelial and mesenchymal elements.
大多数禾本科胚有一片瓣状结构通常称为外胚叶。
Most grass embryos have a flap-like structure known as the epiblast.
中胚叶节脊索类脊椎动物胚胎的中胚层的中间部分，…
The middle zone of the mesoderm of a chordate vertebrate embryo, from which excretory tissue develops.
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