There are several features that you should show:
1. leaf base: is there a distinct petiole? How does the leaf join the stem -
does the petiole flare into "wings" (like N. gracilis), and do these
"wings" run parallel to the stem (again like N. gracilis) or do
they fuse on the opposite side of the leaf (as in N. veitchii).
Since there are many variations, this is a very important feature.
2. pitcher: Many species are very variable. Note that color, shape, and size
are not as important as other features because of the wide variations
between young plants and old plants, and between upper pitchers
and lower pitchers. Lid shape is said to be a more stable factor
(is it heart-shaped, oval, circular, ...?); and also note any unique
features of the lid (glandular boss, filiment, hairs, etc.)
3. If the plant is photographed in the wild, the growth habit should be
noted (does the plant climb trees, is it bush-like, is it an
epiphyte, etc). Also, the types of soils where the plant grows
should be noted (is it rocky, is it acid or alkaline, is there
standing water, etc).
Macfarlaine noted that each species has a number of parallel veins
running on either side of the midrib and this number can be used for
identification. I'm not sure how accurate this could be because the
number of veins can be related to the age and health of the plant.
As for the terrarium at the children's hospital -
1. Find a place to put the aquarium first. Most hospitals I've been to
have nice large windows in most rooms that give enough bright indirect light
to satisfy many CP species.
2. Find a lid with a tight seal so you won't have to water often and that
won't release germs into the clean hospital environment.
3. Species that you can use: D. capensis (may require more light), D. binata
and various forms (should be tolerant of shade), D. pygmaea, Nepenthes
gracilis, most terrestrial Utricularia.
4. These CP should grow well enough without the soil being soaked as when
growing outdoors. Overwatering will produce algae and mold (as well as
producing a stink that the hospital staff will not be happy about).
-- Don Burden New Albany, Indiana USA al423@cleveland.freenet.edu