The type genus Araucaria is derived from "Arauco," a region in central Chile where the Araucani Indians live. This is also the land of the "monkey puzzle" tree (A. araucana), so named because the prickly, tangled branches would be difficult for a monkey to climb. Fossil evidence indicates that ancestral araucaria forests resembling the present-day monkey puzzle date back to the age of dinosaurs. In fact, it has been suggested that the tree's armor of daggerlike leaves may have discouraged enormous South American herbivorous dinosaurs, such as Argentinosaurus weighing an estimated 80 to 100 tons! Another ancient South American species called pino paraná or paraná pine (A. angustifolia) grows in southern Brazil and Argentina. Eight species in this family are represented in the Palomar College Arboretum. Three species of Araucaria are shown in the image to the right. From left: A. angustfolia, A. bidwilli, & A. columnaris.

Palomar College Arboretum

For many years there was disagreement on whether we have both Norfolk Island (Araucaria heterophylla) and Cook pines (A. columnaris) in southern California. In fact, many older references list only the Norfolk Island pine. The Norfolk Island pine typically has well-spaced, tiered, horizontal limbs and a distinctive silouette that is easy to spot from a distance; however, there are also trees with more closely-spaced limbs and a columnar, slender crown resembling the Cook pine. According to Trees of Hawaii by Angela Kepler (1990), most of the trees called Norfolk Island pine in Hawaii are actually Cook pines. They are naturalized throughout the Hawaiian Islands and have been exported as container-grown "Christmas trees" to the U.S. mainland. So it looks like some our southern "California Norfolk Island pines" are actually Cook pines, particularly if they were imported from Hawaii.

Cook pines (Araucaria columnaris) in the northern hemisphere exhibit the peculiar habit of leaning in a southerly direction. In the southern hemisphere the trees commonly lean in a northerly direction. Matt Ritter of California Polytechnic State University, San Luis Obispo and a team of coauthors including Jason W. Johns , Jennifer M. Yost , Dean Nicolle and Boris Igic published an article in Ecology Volume 98 (September 2017) entitled "Worldwide Hemisphere-Dependent Lean In Cook Pines." They studied 256 Cook pines scattered across five continents and collected tree data at 18 locations between latitudes of 7°- 35°north, and 12°- 42°south. The median lean for all trees measured is 2.42 m away from the base, and the median tree height is 18 m, resulting in an 8.05° lean angle. The Leaning Tower of Pisa has a lean angle of 3.99 degrees. Unlike other species of Araucaria, and other conifers in general, their data showed that Cook pines in both hemispheres lean toward the equator. The Ritter team offered several plausible hypotheses for this unusual leaning habit. Cook pines originally come from New Caledonia, a tropical archipelago in the southwest Pacific Ocean. The trees were first classified during Captain James Cook's second voyage to circumnavigate the globe. The leaning habit in cultivated trees is so pronounced that it is often used to separate Cook pines from other similar species of Araucaria. Plant stems exhibit positive phototropism & negative geotropism and tend to grow toward light and away from gravity, while roots exhibit positive geotropism & negative phototropism and grow toward gravity and away from light; however, there are exceptions, such as parasitic mistletoes. Non-vertical shoot growth can be caused by mechanical force from wind or snow. Latitude appears to be a factor in the leaning of Cook pines, the further away the trees grow from the equator, the greater the slant. So possibly leaning has something to do with sunlight. Even if young trees of most species develop a tilt towards the sun, as the tree matures, it tends to correct this asymmetry and grow upwards, unless there's an environmental force preventing this, such as strong prevailing winds in one direction. But for some reason, A. columnaris trees just keep on tilting, no matter how tall they grow. And they even appear to be unique in this regard, because other Araucaria species from New Caledonia can stand up straight no matter where in the world they are planted. According to Ritter, et al (2017), studies on the research plant Arabidopsis thaliana have identified several gene families whose regulation effects phototropic and geotropic growth; however, the mechanisms controlling the expression of these genes are not well understood, especially for woody species. The mechanisms for directional lean in A. columnaris may be related to the incidence angles of annual sunlight, gravity, magnetism, or any combination of these. Another possibility is that the lean is non-adaptive, or even harmful, and may be caused by deleterious alleles in this species. Continued research on this fascinating conifer species may reveal some answers to these perplexing hypotheses, possibly resulting in a new scientific theory on plant growth. Stay tuned!  J.W. Johns, J.M. Yost, D.Nicolle, B. Igic and M.K. Ritter. 2017. Ecology 98 (9): 2482-2484.

Norfolk Island Pine (Araucaria heterophylla)

Norfolk Island Pine (Araucaria heterophylla)

In general, the interval between tiers of limbs is greater on the Norfolk Island pine, particularly on younger trees. In addition, the horizonal limbs are longer than those of the Cook pine. The Cook pine has a slender, spire-like crown with shorter, more closely-spaced horizontal branches. Throughout southern California, there are trees with branching intermediate between the two previous species. The leaf shape and size is variable and not very useful in separating these two species. Some authors have suggested that the bark of cook pine exfoliates into larger flakes. This appears to hold true in the Palomar College Arboretum; however, I have seen trees with intermediate bark flakes. In fact, some trees in southern California with intermediate characteristics between the two species may be hybrids. There are also several different species reported for botanical gardens in southern California.

The genus Agathis includes more than a dozen species of large, resinous trees scattered throughout Australia, New Zealand and the Malay Archipelago. Several species of Agathis are the source of timber and valuable copal varnish, including kauri pine (A. australis), amboina pine (A. dammara) and dammar pine or Queensland kauri (A. robusta). Copals are a group of resins that form particularly hard varnishes. In addition to Agathis, there are New World sources of copal from resinous leguminous trees, including the West Indian locust (Hymenaea courbaril) and several species of Copaifera. Dammars are another group of hard, durable varnishes that turn shiny and transparent when dry. Although some species of Agathis are named dammar, most dammar resins come from tropical Asian trees of the genus Shorea in the Diptocarpaceae. Copals and dammars are used extensively in oil paintings. When painting with oils, colored pigment is squeezed onto a palette and then taken up in a thinning solution of linseed oil mixed with either copal or dammar. The resins "hold" the paint when dry and provide the luminous depth characteristic.

In 1994, David Noble discovered an unknown cone-bearing tree in rugged Wollemi National Park northwest of Sydney, Australia. About 40 trees in deep narrow canyon turned out to be an undescribed species. They were named Wollemi pine (Wollemia nobilis), a remarkable new member of the Araucariaceae. This rare conifer was thought to be extinct because its last fossil record was dated at about two million years ago. Choroplast DNA studies show no discernable genetic variation among the 40 trees. Like the rare Torrey pine (Pinus torreyana) of San Diego County, this is truly a relict population that was more widespread millions of years ago. Because of its small population size, a lot of its genetic diversity has been lost through thousands of years of isolation. The Wollemi pine is a great botanical discovery and is truly a "living fossil." Trees are being propagated from seeds, and will be cultivated in San Diego County like other living fossils, such as the maidenhair tree (Ginkgo biloba) and dawn redwood (Metasequoia glyptostroboides).

For decades Baltic amber has been arbitrarily assigned to an extinct pine (Pinus succinifera) because of the presence of succinic acid; however, IR (infrared spectroscopy) studies show that Baltic amber may be more closely related to resins of broad-leafed conifers of the araucaria family (Araucariaceae). According to J.H. Langenhein (Plant Resins: Chemistry, Evolution, Ecology, and Ethnobotany, 2003), Baltic amber contains pinaceous inclusions (wood fragments and cones) but with araucarian chemical characteristics, so the origin of these vast deposits remains an enigma. Today the only evidence of araucariads in the northern hemisphere comes from amber deposits and petrified wood, such as occurs at Petrified Forest National Park in Arizona. In New Zealand a living araucariad forest of "kauri pine" Agathis australis produces copious amounts of resin that once formed a thriving industry for hard, durable varnishes and linoleum. Large lumps of hardened resin (up to 100 pounds in size) were dug out of the ground in extensive forested areas of North Island. Forests such as this may have once flourished in the Baltic region 60 million years ago. Throughout the world, the most copious resin-producing trees occur in tropical regions. These complex mixtures of terpene resins may serve as a chemical defense against the high diversity of plant-eating insects and parasitic fungi found in the tropics.

Many of the petrified logs at Petrified Forest National Park near Holbrook, Arizona were thought to be related to the araucaria family, including Arizona's state fossil tree Araucarioxylon; however, detailed studies indicate that many of the petrified logs represent different species that are not related to Araucaria.

Petrified Forest National Park in northeastern Arizona contains hundreds of acres of perfectly preserved logs from an ancient conifer forest that dates back to the late Triassic Period (approximately 225 million years ago). The trees of this forest coexisted with dinosaurs. Most of the petrified logs were previously assigned to an extinct species Araucarioxylon arizonicum, a presumed distant relative of Araucaria; however, new evidence indicates that these fascinating deposits of petrified logs represent a broad diversity of conifer species. Streams carried dead logs into this once swampy lowland region where they were buried in sediments rich in volcanic ash. Over countless centuries, the woody tissue has been replaced by minerals and gradually turned into stone. These ancient trees flourished during a time when all of the continents were united into the vast supercontinent Pangea. The area of Petrified Forest National Park was located near the equator, at approximately the latitude of present-day Central America. Although most of the logs do not show cellular detail, there are some permineralized specimens in which minerals permeated the porous cell walls and filled the cell cavities (lumens). Thin sections of these samples viewed under a microscope show remarkable cellular detail.

Although the binomial Araucarioxylon arizonicum has been used in the literature for more than a century, Rodney A. Savidge of the University of New Brunswick (Bulletin of Geosciences Vol. 82 No. 4: 301-328, 2007) states that it is superfluous and therefore an illegitimate name (nomen superfluum). He examined thin sections of the original three specimens (syntypes) housed at the Smithsonian Institute upon which the species was first described by F.H. Knowlton in 1889. He concluded that they represented different species within two new genera of extinct trees. According to the International Code of Botanical Nomenclature, a valid species can have only one type specimen or holotype. Consequently, only one of the three specimens was retained as the new type or lectotype Pullisilvaxylon arizonicum. Savidge examined several other logs previously identified as A. arizonicum and concluded that they also represented additional new genera and species. His extensive anatomical studies indicate that the majority of logs at Petrified Forest National Park do not belong to a single species. It appears that the superfluous name "A. arizonicum" actually refers to a complex of extinct conifers. Based solely on the xylem structure of permineralized wood (including resin canals, rays and tracheid pitting), and without seed cones or DNA evidence, it is difficult to be certain which trees in the complex are ancestral relatives of the araucaria family. According to Dr. Savidge (personal communication, 2008), an immense amount of research into petrified woods is needed before the ancestries leading to modern trees will be clearly understood. At this time it would be purely conjectural to assign a scientific name to most logs in Petrified Forest National Park without detailed microscopic examination of the wood.

Trees of "Araucarioxylon arizonicum" grew to a height 200 feet (61 m) with a trunk diameter from 4 to 9 feet. According to Sidney R. Ash and Geoffrey T. Creber (Paleontology Vol. 43 No. 1: 15-28, 2003), the living tree did not closely resemble any of the present-day Araucaria trees of the southern hemisphere as postulated in past reconstructions. The branches did not occur in whorls as they do in most conifers, instead they grew irregularly along the trunk. Sydney Ash and Rodney Savidge also studied the bark anatomy of Araucarioxylon arizonicum ("The Bark of Late Triassic Araucarioxylon arizonicum from Petrified Forest National Park, Arizona," IAWA Journal 25 No. 3: 349-368, 2004), and concluded that it was quite unlike the banded bark of extant Araucaria heterophylla. These ancient conifers grew in a tropical rain forest with marshes and river lakes, in an environment very different from today's Arizona landscape.

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