The families of gymnosperms

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L. Watson and M. J. Dallwitz

Character list

#1. <Common name>/

#2. <Synonyms:>/

Vegetative

#3. <Habit: pachycaul or leptocaul>/

1. pachycaul/

2. leptocaul <implicit>/

#4. <Evergreen or deciduous>/

1. evergreen/

2. deciduous/

#5. <Habit>/

1. trees/

2. shrubs/

3. vines/

4. a long-lived, woody herbaceous perennial, the woody, tap-rooted stem widening into a concave disc up to a metre across <Welwitschia>/

#6. <Bizarre plant form - Welwitschia>/

1. a bizarre southern African gymnospermous monotypic with a short, woody, unbranched stem bearing only 2 (rarely 3) strap-shaped amphistomatous leaves, the latter continuing to grow from basal meristems throughout the long life of the plant, spreading laterally along the ground, progressively fraying and twisting/

2. plants of conventional form <implicit>/

#7. <Whether exhibiting switch-plant morphology>/

1. Casuarina-like switch-plants photosynthesizing mainly via their grooved and jointed stems, the leaves reduced to small scales which are soon shed/

2. not Casuarina-like switch plants <implicit>/

#8. <Whether exhibiting coralloid masses of apogeotropic roots>/

1. with apogeotropic roots bearing cyanobacteria, born in coralloid masses just above ground level <Cycadales>/

2. without coralloid, cyanobacteria-containing root masses <implicit>/

#9. <Whether plants resinous>/

1. resinous <with resin-containing cells, cavities or canals conspicuous somewhere in the plant>/

2. not resinous/

#10. Main branches <insertion>/

1. spiral <alternate>/

2. whorled/

3. opposite/

#11. The leafy branchlets/

1. flattened in one plane <the leaves 2-ranked by basal twisting: complanate>/

2. not flattened/

#12. The vegetative branch systems <presence or absence of specialized short-shoots: see Notes>/

1. without conspicuously specialised short-shoots/

2. including highly specialised, leaf-bearing short-shoots <spurs>/

All woody spermatophytes, including conifers, exhibit vegetative differentiation involving a hierarchy of dominant, relatively persistent main shoots, and ephemeral shoots which are subject to regular self pruning (with inter-specific variations in the patterns of dominance bestowing upon trees and shrubs their often characteristic growth forms). The term ‘short-shoot’ as generally applied to conifers and well exemplified in the genus Pinus denotes a precisely specialised lateral shoot with highly contracted internodes, bearing a pair or a tight cluster of foliage leaves (needles), which is of limited growth and is shed in its entirety (cf. ‘spur-shoots’ of fruit trees). Some conifers (e.g., Metasequoia) are characterised by short-shoots perhaps better designated ‘phyllomorphs’.

#13. <Presence of phyllodes>/

1. phyllocladineous <flattened stems functioning as leaves>/

2. with normal leaves <not phyllocladineous: implicit>/

#14. Mature <foliage> leaves <simple or compound>/

1. simple/

2. pinnate/

3. bipinnate/

#15. The <cycad> leaflets <venation>/

1. with a prominent midrib and no laterals <Cycadaceae>/

2. with pinnate venation, having a prominent midrib and dichotomously branching laterals <Stangeriaceae>/

3. with numerous parallel or wavy, single or forked longitudinal veins but no prominent midrib <Zamiaceae>/

#16. Mature <foliage> leaves <whether dimorphic>/

1. dimorphic/

2. not dimorphic <implicit>/

#17. Mature <foliage> leaves <form>/

1. broad and flat <and several veined>/

2. linear <and single, single veined: including acicular>/

3. scale-like <single veined>/

4. 2-veined, evidently representing pairs of ‘needles’ united lengthwise <Sciadopitys>/

#18. Mature <foliage> leaves <linear, whether acicular>/

1. acicular <hard and pointed: needle-like>/

2. relatively soft <not acicular>/

#19. Mature <foliage> leaves <organization>/

1. in tight clusters on short-shoots, each cluster with a basal sheath of scales/

2. not <tightly> clustered/

#20. Mature <foliage> leaves <phyllotaxy>/

1. alternate <spiral>/

2. opposite and decussate/

3. whorled/

#21. Longitudinal resin canals <presence in leaves>/

1. present in the leaves/

2. absent from the leaves/

Potentially easily observable in transverse leaf sections, but the data in these descriptions are currently derived entirely from the unsatisfactory sketches in ‘Dallimore and Jackson’.

#22. Longitudinal resin canals <location in transverse sections>/

1. 1 per leaf, this median-abaxial/

2. 2 per leaf, these lateral <median or marginal>/

3. in a horizontal row/

4. in a peripheral ring/

5. in an abaxial arc/

6. in an adaxial arc/

Reproductive organization

#23. <Sexuality>/

1. monoecious/

2. dioecious/

#24. <Possession of flower-like reproductive structures>/

1. the reproductive structures organized like reduced angiosperm flowers <with stamen-like antherophores and exposed, gymnospermous ovules: Gnetales>/

2. the reproductive organization not flower-like <implicit>/

#25. <Comments on female reproductive structures>/

#26. The ovules <whether in cones>/

1. borne in female cones <strobili>/

2. not in cones/

#27. The female cones <woody or berry-like>/

1. woody/

2. fleshy and berry-like/

#28. The seed-cone scales <arrangement>/

1. spirally arranged/

2. opposite and decussate/

3. whorled/

#29. The seed-cone scales <persistent or deciduous>/

1. persistent/

2. deciduous, the cones disintegrating at maturity/

#30. The seed-cone scales <texture>/

1. fleshy/

2. leathery/

3. woody/

#31. The ovules <location>/

1. borne proximal-adaxially on the seed-cone scales <often involving a morphologically complex “ovuliferous scale”>/

2. terminating axes/

3. marginal or in notches, on discrete megasporophylls with sterile tips/

4. axillary <to bracts or seed-cone scales>/

5. borne erect in the centre of the “flowers” <cf. an angiosperm gynoecium>/

#32. The bract-scales <free or fused>/

1. more or less free of the seed-cone scales <or “ovuliferous scales”> in mature cones/

2. extensively fused to the seed-cone scales <or “ovuliferous scales”> in mature cones/

3. not clearly resolvable from the seed-cone scales/

The “seed-scale complexes" of the female cones of living conifers are convincingly interpretable as derivations from specialised, radially organized short-shoots of early fossil forms. These bore the ovules on megasporophylls located basally, succeeded distally by sterile bracts. In some extant forms (notably in Cupressaceae sensu stricto), the original “seed-scale complex” is so reduced that the ovules appear to be borne directly on the bract scales, and vestiges of it remain detectable only during early development of the cone. In other cases (e.g., in Pinaceae), the “complex” is axillary to the bract, and its origins are revealed by its anomalous vascular anatomy. Female cones in the family Taxodiaceae display much variation regarding detectability of the “seed-scale complex”, ranging from the situation in Cunninghamia and Taiwania, where it has almost disappeared, to that in Cryptomeria, where the vestiges of several sterile scales remain readily identifiable in the seed-scale complex via conspicuous distal lobes representing their free apices.

The ovule-bearing arrangements of modern Taxaceae conform with those of early fossils that are readily identifiable with them in showing no evidence of such complications, and the Taxales clearly constitute a sound, phylogenetically distinct group.

#33. The megasporophylls <number of ovules>/

ovuled/

#34. The seed-cone scales <or “ovuliferous scale complexes”: number of ovules>/

ovuled/

#35. The <mature> ovules <orientation>/

1. orthotropus <erect>/

2. anatropous <reflexed>/

#36. The ovules <number of integuments>/

integumented/

#37. <Comments on male reproductive structures>/

#38. Pollen-sacs <number per microsporophyll>/

per microsporophyll/

#39. Pollen <whether with bladders>/

1. with air bladders/

2. without air bladders/

#40. <Comments on pollination>/

#41. Fertilization <whether involving production of motile spermatozoids>/

1. involving spirally flagellate, motile spermatozoids <Cycadales>/

2. not involving motile spermatozoids <implicit>/

Seeds and seedlings

#42. Seeds <whether with fleshy investment>/

1. with a fleshy investment/

2. with no fleshy investment <implicit>/

#43. The fleshy investment <of the seeds, derivation>/

1. receptacular/

2. representing a genuine aril <an outgrowth from beneath the ovule>/

3. developed from the cone-scales/

4. developed from the integument/

#44. Seeds <winged or wingless>/

1. winged/

2. wingless/

#45. Cotyledons <number>/

Wood anatomy

#46. Growth rings <of wood, whether distinct>/

1. indistict/

2. distinct/

#47. Heartwood <whether distinctively coloured>/

1. present and distinctively coloured/

2. present but not distinctively coloured, or absent/

#48. Latewood <whether conspicuous>/

1. not conspicuous <the transition gradual>/

2. conspicuous <the transition abrupt>/

#49. Wood <whether with distinct odour>/

1. with a distinct odour/

2. without distinct odour/

#50. Wood <whether with distinct taste>/

1. with a distinct <bitter or astringent> taste/

2. without distinct taste/

#51. Wood <whether greasy>/

1. greasy to the touch/

2. not greasy/

#52. Wood <whether with dimpled grain>/

1. with dimpled grain/

2. without dimpled grain/

#53. Secondary xylem <presence of vessels>/

1. with vessels/

2. lacking vessels <wood exclusively of tracheids and parenchyma: implicit>/

#54. Tracheids <arrangement of pits>/

1. with alternate bordered pits <in the radial walls>/

2. with opposite and multiseriate bordered pits/

3. with neither alternate nor opposite bordered pits <i.e., bordered pits uniseriate, or lacking?>/

#55. Tracheids <presence of callitroid thickenings>/

1. with callitroid pit-border thickenings/

2. without callitroid pit-border thickenings <implicit>/

#56. Margins of the tori <whether scalloped>/

1. scalloped/

2. not scalloped <implicit>/

#57. Torus extensions <presence>/

1. conspicuously present/

2. absent <implicit>/

#58. Earlywood tracheids <with or without spirals>/

1. with spiral thickenings/

2. without spiral thickenings/

#59. Axial parenchyma <presence>/

1. present/

2. absent/

#60. Axial parenchyma <when present, abundance>/

1. abundant/

2. scarce/

#61. Axial parenchyma <whether zonate>/

1. zonate/

2. not zonate/

#62. Axial parenchyma <presence of nodular or bead-like thickenings on transverse or end-walls>/

1. with nodular thickenings or bead-like on the transverse or end-walls/

2. without nodular thickenings on the transverse or end-walls/

#63. Rays <in TLS, whether exclusively uniseriate>/

1. exclusively uniseriate/

2. not exclusively uniseriate <specify widths>/

#64. Ray tracheids <presence>/

1. regularly present <the rays heterogeneous>/

2. absent or very infrequent <or produced only in response to wounding>/

#65. Ray tracheids <when present, whether dentate>/

1. dentate/

2. not dentate/

#66. Earlywood ray cells <whether with thin horizontal walls>/

1. with horizontal walls thinner than those of the adjacent vertical tracheids above and below the ray/

2. with walls similar in thickness to those of adjacent vertical tracheids/

#67. Latewood ray cells <pitting of horizontal walls>/

1. with pitted horizontal walls/

2. with unpitted horizontal walls/

#68. The pitting <in horizontal walls of latewood rays, strength>/

1. strong/

2. weak/

#69. Ray cells <whether exhibiting indentures>/

1. exhibiting indentures at the corners <best seen in readial sections>/

2. without indentures/

#70. Ray cells <presence of nodular or bead-like thickenings on their end walls>/

1. exhibiting nodular or bead-like thickenings on their end walls <i.e., the vertical walls in radial sections>/

2. without nodular thickenings on their end walls/

#71. Ray tissue <presence of crystals>/

1. exhibiting crystals/

2. without crystals/

#72. Earlywood cross-field pits <configuration>/

1. 1(-3), large and simple (or nearly so)/

2. piceoid/

3. cupressoid/

4. taxodioid/

5. 1–6 pinoid/

#73. Normal vertical resin ducts <presence, exclusive of traumatic resin ducts>/

1. present <nearly always accompanied by horizontal ones in rays>/

2. absent/

#74. The normal resin ducts <thickness of epithelial cell walls>/

1. with at least some thick-walled epithelial cells/

2. with only thin-walled epithelial cells/

#75. The normal resin ducts <number of epithelial cells, in cases where the epithelial cells are thick-walled>/

1. with 5–6 epithelial cells/

2. with 7–12 epithelial cells/

Geography

#76. <Climatic distribution:>/

1. frigid zone/

2. temperate/

3. sub-tropical/

4. tropical/

#77. <World distribution:>/

#78. <Natural geographical distribution (intended for keys only; see NOTES):>/

1. Western and Northern Eurasia, U.S.S.R./

2. Middle East <Turkey to North Africa, and eastwards to Iran>/

3. Mediterranean/

4. Eastern and Southern Asia <including Japan, China, India>/

5. North Africa/

6. Central, East tropical and West tropical Africa/

7. South Africa/

8. Madagascar/

9. Malay Archipelago <including New Guinea>/

10. Australasia <Australia, New Zealand>/

11. Pacific Islands/

12. North America/

13. Central America/

14. West Indies/

15. South America/

16. Arctic/

17. Antarctic/

WARNING. Geographical information can facilitate pursuit of identifications, but must be used with caution. Recorded natural distributions may be incomplete, and numerous ‘exotic’ Gymnosperms are likely to be encountered. Identifications depending on the assumption that specimens are native to the country in they were found may well be wrong, and if there is room for doubt, the Intkey 'tolerance' facility (q.v.) should be invoked. All identifications should on principle be assiduously verified, at least with reference to the full family descriptions and (preferably) pursued to the level of genus or species. The illustrations accompanying the present descriptions are intended to assist to that end.

Cytology

#79. Basic chomosome number, n =/

Taxonomy

#80. <Number of species>/

species/

#81. <Genera included>/

#82. Order/

1. Cycadales/

2. Ginkgoales/

3. Coniferales/

4. Taxales/

5. Gnetales/

Comments

#83. <Comments>/


To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2008 onwards. The families of gymnosperms. Version: 9th April 2015. delta-intkey.com’.

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