There are two kinds of plant collections at the NTBG: living and dead. The living collection includes all the plants that you see in the gardens and greenhouses. That's usually the part that tourists come here to enjoy. But the Garden also houses a collection of dead specimens. I suppose that sounds kind of awful, but what it really means is that they keep thousands of manilla folders in cabinets that each contain a dried and pressed plant specimen. They also have some preserved in alcohol, so that they can maintain the 3D structure of the plant.
The Garden has 62 thousand specimens in the Biological Research Center, and a couple hundred "types." A type is a specimen that is a perfect - or as close to perfect as you can get - example of the species- and they are contained in a special cabinet all their own. This isn't as many as some collections - that might have a half a million specimens - but the Garden claims to have the largest collection of modern Hawaiian plants in the world.
The BRB is Kauai's first LEED certified building. It's filled with recycled wood and natural light, and it's freezing inside. It's necessary so that the samples don't get hot and sticky in the moist Kauai air, and is just one of the many precautions they take here.
The building is what they call a "clean building". You take of your shoes in an airlock in the entry to prevent dirt, and insects form coming in and contaminating the building and its delicate contents. Plant material is handled in what they call a "dirty room" until it is guaranteed free of pests -- samples and even the collections of books are put into a large walk in freezer to kill any pests they might be harboring before they make their way into the permanent collection.
An enormous number of books are housed here - some are rare books dating back to the 1500's - while the rest cover a wide variety of reference material. the public can search the books in person, and the curators here say they are sometimes available through inter library loan. The plant specimens themselves are searchable using a computer, and contain highly detailed photographs that can be used for comparison to living specimens.
Bet you didn't know what went into cataloging the plant diversity in Hawaii did you?