a rare variety of orchid的用法和样例：
- There, in the boundless desert, grows a rare variety of tree called euphrates poplar.
- There， in the boundless desert， grows a rare variety of tree called euphrates poplar.
- The leaf of a rare variety of nanmu tree, just one of the plants considered endangered by rising waters caused by the Three Gorges Dam project in China.
- A variety of food is sold at a supermarket.