, with stems which live above ground only a single
season --2.

2a. Plants with unusual habits or structures, including leafless,
colorless, submerged, floating, parasitic, or hollow-leaved
plants Group 2, =UNUSUAL PLANTS=, p. xxiii.

2b. Ordinary terrestrial or swamp plants, without unusual
structural peculiarities --3.

3a. Leaves parallel-veined (or net-veined in a few species); parts of
the flower usually in threes or sixes, never in fives; wood-fibers
scattered through the stem; seed with one cotyledon. All plants with
definitely parallel-veined leaves may be identified through this
division, unless the parts of the flower are distinctly in fives.
Group 3, =MONOCOTYLEDONES=, p. xxvii.

3b. Leaves net-veined (or parallel-veined in a few species); parts of
the flower usually in fours or fives; wood-fibers arranged in a
circle in the stem; seeds with two cotyledons. All plants with
definitely net-veined leaves may be identified through this
division. Group 4, =DICOTYLEDONES=, p. xxx.

Note:--In order to avoid possible chances of error, many plants have
been treated under both of the above groups. The following hints may
also be useful in distinguishing Groups 3 and 4:

All herbaceous plants with deeply lobed, dissected or compound leaves
may be sought under the Dicotyledones.

All herbaceous plants with five stamens in each flower, or with seven or
more stamens and one ovary in each flower, may be sought under
Dicotyledones.

GROUP 1, WOODY PLANTS

1a. Trees, with erect stem and central trunk, attaining a height of 6 m.
(20 ft.) or more --2.

1b. Shrubs or woody vines, without true tree habit, or attaining heights
of less than 6 m. (20 ft.) --52.

2a. Key for use in earliest spring, for trees which have flowers
but no leaves --3.

2b. Key for use with trees bearing leaves --21.

3a. Flowers in catkins, without brightly colored or petal-like parts
--4.

3b. Flowers not in catkins, either with or without petals --14.

4a. Leaf-scars and lateral buds 2-ranked, i. e., in two
longitudinal rows with the third leaf above the first --5.

4b. Leaf-scars and buds in three or more longitudinal rows --9.

5a. From 1 to 3 bud-scales visible on each leaf-bud