Callitris is a genus of coniferoustrees in the Cupressaceae (cypress family). There are 16 recognized species in the genus, of which 13 are native to Australia and the other three (C. neocaledonica, C. sulcata and C. pancheri) native to New Caledonia.[1] Traditionally, the most widely used common name is cypress-pine,[3] a name shared by some species of the closely related genus Actinostrobus.[4]
Description
They are small to medium-sized trees or large shrubs, reaching 5–25 m (16–82 ft) tall (to 40 m (130 ft) in C. macleayana). The leaves are evergreen and scale-like, but young seedlings have needle-like leaves; in C. macleayana, needle-like leaves are found mixed with scale leaves throughout the tree's life. The scales are arranged in six rows along the twigs, in alternating whorls of three (often in whorls of four in C. macleayana).
The male cones are small, 3–6 mm (0.12–0.24 in) long, and are located at the tips of the twigs. The female cones start out similarly inconspicuous, maturing in 18–20 months to 1–3 cm (0.39–1.18 in) long and wide, globular to ovoid (acute in C. macleayana), with six overlapping, thick, woody scales, arranged in two whorls of three (often 8 scales in C. macleayana). The cones remain closed on the trees for many years, opening only after being scorched by a bushfire; this then releases the seeds to grow on the newly cleared burnt ground.
Taxonomy
The genus is divided into two sections, with the atypical C. macleayana in sect. Octoclinis, and all the other species in sect. Callitris. Some botanists treat C. macleayana in a separate genus, as Octoclinis macleayana. C. macleayana is also distinct in occurring in rainforest on the east coast of Australia; the other species all grow on dry sites.
The closest relative of Callitris is Actinostrobus from southwest Western Australia, which differs in its cones having several basal whorls of small sterile scales. A 2010 study of Actinostrobus and Callitris places the three species of Actinostrobus within an expanded Callitris based on analysis of 42 morphological and anatomical characters.[5]
In 2010, early Oligocene fossilised foliage and cones of Callitris were unearthed near the Lea River in Tasmania. The fossils were given the name Callitris leaensis and represent the oldest known representative of the genus.[6]
Callitris columellaris – south-east QLD (coastal); naturalised in Hawaii and southern Florida. Previously synonymous with C. glaucophylla, C. endlicheri and C. intratropica.
The wood of cypress-pines is light, soft and aromatic. It can be easily split and resists decay; cypress-pine is also termite resistant. It is used to make furniture, indoor and outdoor paneling, and fence posts. Cypress-pines are occasionally planted as ornamental trees, but their use is restricted by the high risks imposed by their very high flammability in bushfires.
Previously a plantation of C. intratropica was established outside of Darwin for use in house construction.[11] After Cyclone Tracey it was realised that the timber did not resist strong winds and the plantation was abandoned. The trees are now used for the production of a blue essential oil, rich in guaiol and chamazulene (the blue compound). A number of therapeutic effects are attributed to the essential oil, including antimicrobial and anti-inflammatory effects.
References
^ a b cKew World Checklist of Selected Plant Families
^Byng, J. W. (2015). The Gymnosperms Handbook: A practical guide to extant families and genera of the world. Plant Gateway Ltd.
^Australian Plant Names Index, retrieved 8 December 2015
^Eckenwalder, J.E. 2009. Conifers of the World: The Complete Reference. Timber Press. p. 122-124
^Piggin, J.; Bruhl, J. J. (2010). "Phylogeny reconstruction of Callitris Vent. (Cupressaceae) and its allies leads to inclusion of Actinostrobus within Callitris". Australian Systematic Botany. 23 (2): 69–93. doi:10.1071/SB09044.
^Paull, Rosemary (2010), "Early Oligocene Callitris and Fitzroya (Cupressaceae) from Tasmania", American Journal of Botany, 97 (5): 809–820, doi:10.3732/ajb.0900374, PMID 21622446
^Stull, Gregory W.; Qu, Xiao-Jian; Parins-Fukuchi, Caroline; Yang, Ying-Ying; Yang, Jun-Bo; Yang, Zhi-Yun; Hu, Yi; Ma, Hong; Soltis, Pamela S.; Soltis, Douglas E.; Li, De-Zhu; Smith, Stephen A.; Yi, Ting-Shuang; et al. (2021). "Gene duplications and phylogenomic conflict underlie major pulses of phenotypic evolution in gymnosperms". Nature Plants. 7 (8): 1015–1025. bioRxiv10.1101/2021.03.13.435279. doi:10.1038/s41477-021-00964-4. PMID 34282286. S2CID 232282918.
^Jones, Graham; Sadgrove, Nicholas (March 2015). "A Contemporary Introduction to Essential Oils: Chemistry, Bioactivity and Prospects for Australian Agriculture". Agriculture. 5 (1): 48–102. doi:10.3390/agriculture5010048.
