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Keys

Keys are devices used to identify plants. A typical key provides the user with a series of two (or more) botanical statements, called leads. A lead may have more than one statement; the first is the most important but additional statements are added if the first statement is difficult to use or will only be seen at one time of the year (for example, flowers, or fruit). You select the lead that best describes the plant at hand, then follow this lead to additional leads. With each subsequent lead, the choice of representative plants is narrowed down, until ultimately you are left with the one plant that matches the series of leads. Typically there are several sets of keys-one to identify the plant family, another to identify the genus, and a third to identify the species. There also may be separate keys based on flowers, fruits, or leaves.

There are two common types of keys: indented and bracketed. In indented keys, each set of leads is indented, with subordinate leads indented immediately below. In bracketed keys, each set of leads is placed side-by-side.

Keys to the Species of Rhododendron in the New York Metropolitan Region

The following are examples of an indented and a bracketed key to the same group of species.

An Indented Key

1. Leaves evergreen
   2. Leaves densely hairy below, the hairs
      orange or white; the flower deeply cleft
      and appearing to have separate petals...
      ..............Rhododendron groenlandicum
   2. Leaves hairless; the flower with five petals
      fused into a shallowly lobed tube.......
      ....................Rhododendron maximum
1. Leaves deciduous
   3. Flowers with three petals fused together
      and two petals not fused, flowers pink...
      ...................Rhododendron canadense
   3. Flowers with all the petals fused
      together, flowers white to pink..........
      4. Flowers appearing after the leaves
      have expanded (essentially when all of
      the leaves have unfolded, and the
      vegetative bud scales are absent)........
      ....................Rhododendron viscosum
      4. Flowers appearing before or with the
      leaves (when at least some of the leaves
      are still folded or the vegetative bud scales
      are still present)
      5. Floral bud scales hairless; flower stalks
      without both short and long hairs, usually
      only with long hairs; leaves hairless or with
      a few scattered one-celled hairs.............
      .................Rhododendron periclymenoides
      5. Floral bud scales densely covered
      with one-celled hairs; flower stalks
      with both short and long hairs; leaves
      moderately to densely covered with one-celled
      hairs on the mlower side.....................
      ....................Rhododendron prinophyllum

A Bracketed Key

1. Leaves evergreen...............................2
1. Leaves deciduous...............................3

2. Leaves densely hairy below, the hairs orange
   or white; the flower deeply cleft and appearing
   to have separate petals.........................
   ......................Rhododendron groenlandicum
2. Leaves hairless; the flower with five petals
   fused into a shallowly lobed tube...............
   ............................Rhododendron maximum
   
3. Flowers with three petals fused together and
   two petals not fused, flowers pink..............
   ..........................Rhododendron canadense
3. Flowers with all the petals fused together,
   flowers white to pink..........................4
   
4. Flowers appearing after the leaves have
   expanded (essentially when all of the leaves
   have unfolded, and the vegetative bud scales
   are absent).................Rhododendron viscosum
4. Flowers appearing before or with the leaves
   (when at least some of the leaves are still
   folded or the vegetative bud scales are still
   present).......................................5

5. Floral bud scales hairless; flower stalks
   without both short and long hairs, usually only
   with long hairs; leaves hairless or with a few
   scattered one-celled hairs......................
   .....................Rhododendron periclymenoides
5. Floral bud scales densely covered with one-celled
   hairs; flower stalks with both short and long hairs;
   leaves moderately to densely covered with one-celled
   hairs on the lower side.........................
   ........................Rhododendron prinophyllum