"All that exists is, in a sense, the seed of what will be born from it." -- Marcus Aurelius
|First year cone of
Mexican Red Pine|
(Hartweg's Pine - Pinus hartwegii).
In common with other members of the class Gymnospermae, pine trees have no flower or fruit. Rather, the ovule (and later the seed) are "naked" (gymno = naked, in Greek) and are, in all members of the Pinaecae family, wedged between the scales of a woody "cone," so named because it is generally cone-shaped. The cone bearing the female gametes is larger and is commonly recognized simply as the pine cone, but also can be called the female cone or megasporangiate strobilus.
(Male or Pollen cones)
Red Pine (Pinus resinosa).
In some texts the name for the structure bearing the male gamete also incorporates the name cone, such as the "male cones" or "pollen cones," but these structures are clustered, are much smaller and deteriorate quickly. They really shouldn't be called cones, although there is not a good common term for them. These "male cones" are properly called microsporangiate strobili, which is not an easy common usage term. Also the term "catkins" (from cat tails) which is used in the case of the angiosperms doesn't describe them well and is not commonly used for gymnosperms. The pollen shed from the microsporangiate strobili is carried to the megasporangiate strobili (cones) by the wind. Pines are not pollinated by insects.
|Early second year cone
of Knobcone Pine|
Pine cones (herein referring only to the true female cones) have a peduncle (stem) which attaches to the branch (usually the upper branches) of the tree and this continues through the entire length of the cone as the rachis (axis). Multiple cone scales arise along the length of the rachis in a helical fashion to give the cone most its mass and characteristic external appearance. The cone scales each carry two ovules which usually develop into seeds on their ventral (the side closer to the distal end of the cone) surfaces. Hence these scales are also called ovuliferous scales or seed scales. Lack of pollination, genetic defects or other mishaps may result in sterile (or no)seeds. A smaller bract scale subtends and merges with the cone scale dorsal surface and is quite inconspicuous. (The bract scales can be clearly seen on Douglas fir cones because they are longer than the seed scales and protrude as the familiar trident tags.)
|Pairs of seeds on the
seed (ovuliferous) scales|
of a Gray Pine Cone
(or Digger Pine, Pinus sabiniana).
(tip of cone cut away)
The seed scale has two parts. The first is the umbo which is the first year's growth and distal most portion of the the two year old cone's scales. The umbo in many of the yellow pines (Diploxylon) has a sharp spike ("prickle"). The second part of the seed scale grows in the second year (after fertilization) of the seed scale and is called the apophysis. Pine cones reach maturity in two years in almost all species. The exceptions are Pinus leiophylla (including subspecies chihuahuana) and Pinus pinea which require three years; Pinus torreyana and maximartinezii require about 2 1/2 years for cone maturation.
microsporangiate strobili (upper, tan color)
megasporangiate strobili (lower, purple).
The size and form of pine cones are important diagnostic features in species identification. They vary in length from approximately 4 to 6.5 cm. (1.5 to 2.5 ") in the case of Pinus banksiana and Pinus teocote to 30 to 50 cm. (12 to 20") (and occasionally up to 70 cm., or 28"!) in Pinus lambertiana, the famous Sugar Pine from California. The heaviest cones are borne by another California native, Pinus coulteri ( 1 to 2.25 kg., or 2.2 to 4.9 lbs!). Being struck on the head by a falling Coulter pine cone is reputed to be a potentially fatal experience.
|Cones of Eastern White
Pine (Pinus stobus) [above]|
and Sugar Pine (Pinus lambertiana) [below].
The cones of the subgenus Haploxylon (White Pines) are easily distinguished from those of the subgenus Diploxylon (Yellow Pines). The White Pines (except for the Pinyon Pines) have scales with a terminal umbo (the distal margin of the seed scale is free) and the Yellow Pines and Pinyon Pines have scales with a dorsal umbo (distal margin of the seed scale is appressed). The White Pine's cones have no prickle on the umbo and many of the Yellow Pine's cones do. Also, the White Pine's cones have a long slender peduncle and the Yellow Pine's cones have short stout peduncles.
|Cones of (clockwise
Loblolly Pine (Pinus taeda)
Jack Pine (Pinus banksiana)
Gray Pine [with seeds] (Pinus sabiniana)
Knobcone Pine (Pinus attenuata)
The two seeds carried on the ventral surface of the seed scale may be released from the cone when the cone's scales flare outward, i.e., the cone opens, when the cone reaches maturity after two years and then most cones fall to the ground. But sometimes the seeds remain on the seed scale until some time after the pine cone has fallen. And in some species the cone remains closed and tightly attached to the tree for many years, i.e., they are serotinous (serotina = late, in Latin). Some pine's seeds are disseminated by birds (see the book Made for Each Other; A Symbiosis of Birds and Pines).
In many pine species each seed has a wing (which aids in dissemination by the wind) and the type of attachment of the wing to the seed varies. In Pinyon Pines (subsection Cembroides) and in the Big-cone Pinyon Pines (subsection Pinceana) the seeds are wingless and in the stone pines (subsection Cembrae) the seed wing is merely a narrow rim.. In all other White Pines (subgenus Haploxylon) the wing is firmly attached to the seed (adnate attachment). In the Yellow Pines (subgenus Diploxylon) the wing is attached more loosely (articulate attachment).
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