well-developed

The micrib belonging to bicollateral bundle is well developed.The bundle sheath is composed of idioblasts.

主脉发达，有异细胞组成的维管束鞘，具双生韧。

Cheeks--Well developed chewing muscles, but not so much that "cheekiness" disturbs the rectangular head form.

颊咬合肌发达，但不能太夸张以至于成“厚脸”，而破坏了矩形头的整体外。