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Practice 9

Complete the text below by choosing the

correct prepositions

Orchids are the largest and most diverse ………. the

flowering plant families, with over 800 described genera

and 25,000 species. Some sources give 30,000 species, but

the exact number is unknown since classification differs

greatly ………. the academic world. Revisions of different

genera occur ………. a monthly basis and this will increase

………. the growing use ………. genetic research and

biochemistry. More than 100,000 hybrids and cultivars,

produced ………. horticulturists, have been created ……….

the introduction of tropical species ………. the 19th century.

The Kew "World Checklist of Orchids" includes about 24,000

accepted species. About 800 new species are added each

year. Orchids, along ………. grasses, are considered

examples ………. the most advanced (derived) floral

evolution through their interactions ………. pollinators and

their symbiosis ………. orchid mycorrhizal fungi.

Source: http://en.wikipedia.org/wiki/Orchids