View source for Key to Families of Gymnosperms

{{Treatment/ID
|accepted_name=Key to Families of Gymnosperms
|accepted_authority={{Treatment/AuthorLink|
James E. Eckenwalder}}{{Treatment/AuthorLink|John W. Thieret}}
|hierarchy=Key to Families of Gymnosperms
|volume=Volume 2
}}<!--

--><p>In the key below, the term "needlelike" as applied to gymnosperms in the flora is descriptive of those leaves that are evergreen (except in Larix and Taxodium), more or less linear, and either more or less flattened (e.g., Abies) or not (e.g.,Pinus)</p>
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==Key==
<div class="treatment-key-group">
  
{| class="wikitable fna-keytable"
|-id=key-0-1
|1
|Leaves pinnately compound, leaflets linear; dioecious; stem below ground, or its leaf-bearing apex exposed; Florida and Georgia.
|[[Zamiaceae|Zamiaceae]]
|-id=key-0-1
|1
|Leaves simple, fan-shaped, needlelike, or scalelike; dioecious or monoecious; stem aboveground; widespread.
|[[#key-0-2| > 2]]
|-id=key-0-2
|2
|Leaves deciduous, fan-shaped, dichotomously veined; ovules 2 at ends of long stalks, often only 1 maturing.
|[[Ginkgoaceae|Ginkgoaceae]]
|-id=key-0-2
|2
|Leaves mostly evergreen (deciduous in Larix and usually in Taxodium, often ephemeral and not photosynthetic in Ephedra), needlelike or scalelike, not dichotomously veined; ovules (and seeds) 1–20 on cone scales or 1 on short stalks.
|[[#key-0-3| > 3]]
|-id=key-0-3
|3
|Longest internodes 2–10 cm (shorter at bases of branches); pollen cones compound, each sporangiophore subtended by a pair of bracteoles; seeds inserted on axis of seed cone, subtended by several pairs or whorls of papery, herbaceous, or fleshy bracts; shrubs (sometimes clambering), neither resinous nor fragrant; dry areas in w United States (se Texas to Oregon and California).
|[[Ephedraceae|Ephedraceae]]
|-id=key-0-3
|3
|Longest internodes 0–1 cm; pollen cones simple, the individual sporophylls not bracteate (usually few sterile bracts at base of cone); seeds inserted on scales of seed cone, scales woody (fleshy and coalescent in Juniperus), or the seeds solitary and not enclosed by bracts or scales in Taxaceae; shrubs or trees, usually resinous and fragrant; widespread.
|[[#key-0-4| > 4]]
|-id=key-0-4
|4
|Seed 1, subtended by but not concealed by inconspicuous sterile bracts, with fleshy or juicy arils; leaves needlelike, spreading in 1 plane ("2-ranked") (except on erect shoots), without resin canals.
|[[Taxaceae|Taxaceae]]
|-id=key-0-4
|4
|Seeds 1–400 in woody or fleshy cones, enclosed by conspicuous cone-scales, without arils (if cones fleshy then leaves not spreading in 1 plane); leaves needlelike or scalelike, spreading in 1 plane or not, with or without resin canals.
|[[#key-0-5| > 5]]
|-id=key-0-5
|5
|Foliage leaves needlelike, alternate or fascicled, individually abcising from branchlets when shed (except that fascicles in Pinus are shed as units); cone scales imbricate, seeds 2 per scale.
|[[Pinaceae|Pinaceae]]
|-id=key-0-5
|5
|Foliage leaves needlelike or scalelike, alternate, opposite, or whorled, persistent on branchlets (but most branchlets shed with age); cone scales valvate or imbricate (if imbricate then leaves opposite and scalelike), seeds 1–20 per scale.
|[[Cupressaceae|Cupressaceae]]
|}
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