I visited Victor Harbor, South Australia from August 2023 till September 2023, arriving in late winter and observed spring weather from 1 September 2023. While looking at birds I also noticed plants blooming and brightening the roadsides and parks. One day I noticed some pink galahs (Eolophus roseicapilla) tackling the winged seeds of the Norfolk Island Pine (Araucaria heterophylla) scattered on park grounds. This motivated me to look for cones usually associated with pine trees. To my surprise I found none. This observation set in motion my endeavour to look for cones growing on other mature Norfolk Island Pine trees, which are abundant in Victor Harbor.
I started noticing trees with slim, structures hanging down. There were green ones on the trees and a lot of brown ones that had been shed onto the ground. I took the brown ones home and discovered that they were male cones (male strobili/ staminate strobili), still shedding copious amounts of yellow pollens ( Images 5-12, video). When I scrutinized more trees, I noticed upright, green globose-shaped structures amongst the twigs. These resemble traditional microphones used during stage performances. They can also be described as truncated wafer cones with a scoop of ice-cream each. These female cones (female strobili/ovulate strobili) were at different stages of development. (Images 13 – 30).
I noted that some trees only had male cones, some only had female cones and yet others had both male and female cones. Male cones were abundant on the lower branches and female cones were abundant on higher branches. But some trees had a few female cones on lower branches and male cones on higher branches too. According to the Heritage Listed Trees of Victor Harbor lodged with the State of South Australia, “The planting of Norfolk Island Pines as memorial trees in South Australia was begun in Victor Harbor in 1917. These trees, now almost 100 years old, are the earliest, and a rare surviving, South Australian example of a World War 1 arboreal memorial.” I am unsure what determines the formation of male and female cones: Are the trees dioecious? Are some trees monoecious? Genetic determination? Age of trees? Abiotic factors?
Araucaria and pine trees separated evolutionarily long ago, still sharing some features. Araucariaceae dates back to the Triassic period (250 million years ago) but they are only found naturally in the Southern Hemisphere now. Pine fossils date back to the Cretaceous period (140 million years ago). Read the following post about the living fossil, Wollemi Pine, discovered in New South Wales in 1994 . https://www.livescience.com/planet-earth/plants/mystery-of-living-fossil-tree-frozen-in-time-for-66-million-years-finally-solvedAraucaria cones disintegrate and the winged seeds are carried away by wind whilst pine trees usually drop whole cones onto the ground. Pine seeds lodged in the space between cone scales are then eaten by seed-eaters or drop out when the cones disintegrate naturally on the ground.
Image 1: Three beautiful Norfolk Island Pine trees growing near the horse tram station. 22 August 2023.Image 2: More Araucaria heterophylla trees framed against houses at Encounter Bay. 20 August 2023.Image 3: Branches grow from the tree trunk in whorls, forming platforms. These trees are popular as potted Christmas trees. 20 August 2023.Image 4: Terminal growing point of a Norfolk Island Pine. 20 August 2023.Image 5: Young male strobili growing downwards from branches. 21 August 2023.Image 6: Close-up of a young male strobilus with the leaf-like microsporophylls pressed close against each other. The leaf-like parts of cones and floral parts of flowering plants are modified leaves compressed along a short central axis. 21 August 2023.Image 7: Brown male cones still attached to the twigs. 21 August 2023.Image 8: Close-up of the brown male cones show the microsporophylls have separated from each other. 21 August 2023.Image 9: I hold up a male cone with a slightly displaced microsporophyll. 7 September 2023.Image 10: The displaced microsporophyll is removed from the cone and placed on a table mat. The microsporangia, called stamens in flowering plants, are devoid of pollen grains now. 7 September 2023.Image 11: The microsporophyll in Image 10 seen under different lighting conditions. 7 September 2023Image 12: Copious amounts of yellow pollen grains fell out of this short male cone. During the few days that I kept the fallen brown male cones at my residence, my family had sneezing bouts and runny noses. I conjectured that the pollen grains were responsible for the sneezing. The same happened after walking in the parks. Araucaria plants are wind-pollinated. 7 September 2023.
Then I proceeded to shake the male cone lightly. More pollens fell out onto the mat. 7 September 2023.Image 13: Two young, upright female cones. 2 September 2023.Image 14: A young female cone growing on a low branch. 6 September 2023.Image 15: More than 20 female cones developing near the growing tip. 29 August 2023.Image 16: Another perspective of the tree in Image 15. More female cones on other branches. 29 August 2023.Image 17: Closer view of female cones on other branches. 29 August 2023.Image 18: Closer view of two female cones showing the megasporophylls edged with a sharp spike each. 2 September 2023.Image 19: A lone female cone. 21 August 2023.Image 20: A young female cone with a cluster of developing female cones below it. 21 August 2023.Image 21: A close-up view of the cone scale spines turning brown at the tips. 2 September 2023.Image 22: An older female cone, probably from the year before, turning dry and brown from the terminal end. The cones take about 18 months to mature. 6 September 2023.Image 23: A maturing female cone. (s)seed, (cs)cone scale. The seed is not fully adnate to the cone scale. 6 September 2023.Image 24: The whole female cone has turned brown while still attached to the tree. 22 August 2023.Image 25 : A newly disintegrating female cone nestled in a bed of green twigs. The twigs are lined spirally with short awl-shaped leaves. 21 August 2023.Image 26: The axis of this female cone is disintegrating at the same rate as the seeds are shed. The seeds are dispersed in a spiral sequence. 22 August 2023.Image 27: This close-up view of the disintegrating female cone shows a bulging seed with its two flattened wings on either side. The fully developed seeds are adnate to the upper surface of each woody cone scale (the megasporophyll before pollination, fertilisation and seed formation). 6 September 2023.Image 28: This female cone is disintegrating and has lost most of its winged seeds. 6 September 2023.Image 29: This female cone has a few more seeds to shed. 2 September 2023.Image 30: This disintegrating female cone is tilted from the vertical position. Viewed from just below the female cone. 21 August 2023.Image 31: Winged seeds of different sizes that I picked up from the ground. The mature seeds are fully adnate to cone scale thus the overhang is absent in all of them. 7 September 2023.Image 32: The sharp spine on the outer edge of each cone scale points upwards but curls downwards now . This immature seed is not fully adnate to the cone scale, forming an overhang on the upper surface of the cone scale. 7 September 2023.Image 33: The sharp spine turning brown progressively along its length. Note the overhang on the upper surface of the cone scale. 7 September 2023.Image 34: The wings of this seed are breaking down along the thinner edges. 7 September 2023.Image 35: The remnant of a seed eaten by a pink galah. For a few days I tried to pry the seed out from a complete winged seed with the help of scissors, knives and pliers but failed. The pink galahs are marvelous at this job. 7 September 2023.
All these observations bear out a characteristic of Araucaria that contrasts with pines. I finally understood why I could not find any female cones on the ground.
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