Why did the Congress establish the U.S. Botanic Garden?

The U.S. Botanic Garden is America’s plant museum. (26) Congress established the Botanic Garden as a center for the science of growing things. But the Garden is also a center of beauty.
   (28) The Botanic Garden has twenty-five thousand plants in its collection. (27) Visitors can see many of them in the Garden’s public Conservatory. It is a large stone and glass structure near the U.S. Capitol building.
   There is a titan arum plant at the U.S. Botanic Garden. It is called the "corpse plant" because its flower smells something like a dead body. Everywhere you look in the Conservatory, something appeals to your eyes. (28) A visitor can move seemingly from one part of Earth to another in just a few seconds. A short walk takes you from desert to thick forest.
   (28) The Conservatory offers examples of plants that provide the makings of medicine. It also has plants of special interest to children. (28) Rare and endangered plants occupy a place all their own.