遗嘱中规定，这座房子将在他孙子成年后归还给他，作为他的复归权。

The will stated that the house would return to him as a ___reversionary right when his grandson came of age.

这种植物的叶子在干旱时会表现出返祖现象，变回更原始的形状。

The leaves of this plant show a ___reversionary tendency during drought, returning to a more primitive shape.