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3. Pinaceae Lindley

Pine Family

John W. Thieret

Trees (occasionally shrubs), evergreen (annually deciduous in Larix ), resinous and aromatic, monoecious. Bark smooth to scaly or furrowed. Lateral branches well developed and similar to leading (long) shoots or reduced to well-defined short (spur) shoots ( Pinus , Larix ); twigs terete, sometimes clothed by persistent primary leaves or leaf bases; longest internodes less than 1cm; buds conspicuous. Roots fibrous to woody, unspecialized. Leaves (needles) simple, shed singly (except whole fascicles shed in Pinus ), alternate and spirally arranged but sometimes proximally twisted so as to appear 1- or 2-ranked, or fascicled, linear to needlelike, sessile to short-petiolate; foliage leaves either borne singly (spirally) on long shoots or in tufts (fascicles) on short shoots; juvenile leaves (when present) borne on long shoots, scalelike; resin canals present. Pollen cones maturing and shed annually, solitary or clustered, axillary, ovoid to ellipsoid or cylindric; sporophylls overlapping, bearing 2 abaxial microsporangia (pollen sacs); pollen spheric, 2-winged, less commonly with wings reduced to frill (in Tsuga sect. Tsuga ), or not winged (in Larix and Pseudotsuga ). Seed cones maturing and shed in 1--3 seasons or long-persistent, sometimes serotinous (not opening upon maturity but much later: Pinus ), compound, axillary, solitary or grouped; scales overlapping, free from subtending included or exserted bracts for most of length, spirally arranged, strongly flattened, at maturity relatively thin to strongly thickened and woody (in Pinus ), with 2 inverted, adaxial ovules. Seeds 2 per scale, elongate terminal wing partially decurrent on seed body (wing short or absent in some species of Pinus ); aril lacking; cotyledons 2--12[--18].

Genera 10, species ca. 200 (6 genera, 66 species in the flora with 64 natives and 2 naturalized): almost entirely in the Northern Hemisphere.

The Pinaceae, with a fossil record extending back to the Cretaceous (C.N. Miller Jr. 1988), constitute a clearly defined natural taxon, the basic delimiting features of which are seen in the mature seed cones: bract-scale complexes consisting of well-developed scales that are free for most of their length from the subtending bracts, two inverted ovules on the adaxial face of each scale, and usually an obvious seed wing that develops from the cone scale. The 10 genera, too, are clearly defined.

The cones of certain members of the Pinaceae remain on the tree and closed for several to many years until a stimulus (often fire) causes them to open and shed their seeds. This condition, known as serotiny (adjective, serotinous), is seen in various pines (e.g., Pinus attenuata , P . banksiana , P . contorta ).

This primarily Northern Hemisphere family extends south to the West Indies, Central America, Japan, China, Indonesia, the Himalayas, and North Africa. The family is dominant in the vegetation of large regions including, in the flora area, forests of the boreal and Pacific regions, of the western mountains, and of the southeastern coastal plain. Only one species of the family, Pinus merkusii , crosses the equator (in Sumatra).

Members of the Pinaceae are of major economic importance as producers of most of the world's softwood timber. Additionally, they are sources of pulpwood, naval stores (e.g., tar, pitch, turpentine, etc.), essential oils, and other forest products. All members of the family present in the flora, especially pines, are of varying importance to wildlife for food and cover. Many species, including most of the genera, are grown as ornamentals and shelter-belt trees and for revegetation. Most commonly seen in cultivation in the flora area are species of Abies , Cedrus , Larix , Picea , Pinus , Pseudotsuga , and Tsuga , each of these genera being represented by numerous cultivars. Keteleeria and Pseudolarix are mainly botanical garden subjects. Cathaya , the most recently described genus (1958), is apparently not yet in cultivation in North America.

Among the vegetative features useful for identification of some genera of Pinaceae are the leaf scars. These are best observed on those portions of living branchlets from which leaves have fallen.

SELECTED REFERENCES

Burns, R.M. and B.H. Honkala. 1990. Silvics of North America. 1.Conifers. Washington. [Agric. Handb. 654.] Canadian Forestry Service. 1983. Reproduction of conifers. Forest. Techn. Pub. Canad. Forest. Serv. 31. Farjon,A. 1990. A Bibliography of Conifers. Königstein. [Regnum Veg. 122.] Hosie, R.C. 1969. Native Trees of Canada, ed. 7. Ottawa. Pp. 83--95. Little, E. L. Jr. 1979. Checklist of United States Trees (Native and Naturalized). Washington. Pp. 33--36. [Agric. Handb. 541.] Silba,J. 1986. Encyclopaedia Coniferae. Phytologia Mem. 8: 1--127.


1 Leaves on year-old and older branches borne either in clusters (fascicles) of 2-5(-6), each cluster scaly-sheathed at base at least when young, or in clusters of 10-60 on short (spur) shoots, clusters not scaly-sheathed.   (2)
+ Leaves borne singly along branches, not scaly-sheathed at base or, if so when young, then terete.   (3)
       
2 (1) Leaves in clusters of (1-)2-5; scales of seed cones with thickened apical portion (apophysis) bearing terminal or central, scarlike to raised umbo and, often, prickle or claw.   6 Pinus
+ Leaves in clusters of 10-60 on short (spur) shoots; scales of seed cones without apophyses, umbos, and prickles.   4 Larix
       
3 (1) Leaves terete, scaly-sheathed at base when young; scales of seed cones with thickened apical portion (apophysis) bearing central, scarlike umbo; mature trees mostly round topped, usually less than 15 m; arid areas in w North America.   6 Pinus
+ Leaves neither terete nor scaly-sheathed; scales of seed cones lacking apophyses and umbos; mature trees of various habit, often conic, often more than 15 m; habitat various, but mostly not of arid areas in w North America.   (4)
       
4 (3) Twigs conspicuously roughened by decurrent, spreading or appressed, peglike projections that persist after leaves fall.   (5)
+ Twigs not roughened by decurrent peglike projections, but, if roughened at all, by more or less circular to elliptic leaf scars, these flush with twig surface, slightly depressed, slightly raised evenly all around, or slightly raised on proximal side only.   (6)
       
5 (4) Leaves sharp-pointed or less often bluntly acute, somewhat flattened or more or less square in cross section, sessile; leading shoot erect.   5 Picea
+ Leaves rounded or notched, flattened, abruptly narrowed to petiolelike base; leading shoot typically drooping.   2 Tsuga
       
6 (4) Leaf scars circular to elliptic, flush with twig surface, slightly depressed, or slightly raised evenly all around; seed cones erect, at least before full maturity, not falling whole but scale by scale, each cone axis persisting as an erect "spike" on branch, the fan-shaped scales often littering ground under tree, bracts protruding beyond scales or not.   1 Abies
+ Leaf scars transversely elliptic, slightly raised on proximal side only, thus tilted; seed cones pendent, falling whole, bracts protruding beyond scales.   3 Pseudotsuga

Lower Taxa


 

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