external phloem造句

例句與造句

Internal phloem is mostly primary, and begins differentiation later than the external phloem and protoxylem, though it is not without exceptions.
In some eudicot families ( Apocynaceae, Convolvulaceae, Cucurbitaceae, Solanaceae, Myrtaceae, Asteraceae, Thymelaeaceae ), phloem also develops on the inner side of the vascular cambium; in this case, a distinction between "'external phloem "'and "'internal phloem "'or "'intraxylary phloem "'is made.
It's difficult to find external phloem in a sentence. 用external phloem造句挺難的