Alternatively, the plants can grow with their roots in a substratum such as sand, vermiculite, or LECA granules.

除此之外，植物也可以在土壤中生长，如沙子、蛭石或莱卡颗粒。

In this there was a substratum of truth.

这里面有一个的基础。

Firmly narrowing upward from this wealthy but inconspicuous substratum was the compact and dominant group which the Mingotts, Newlands, Chiverses and Mansons so actively represented.

从这个富有但不显眼的底层坚定向上缩小的是明戈特、纽兰兹、奇弗斯家族如此积极代表的紧凑而占主导地位的群体。