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We had thought that we could be able to advance the Wellingtonia count during our visit to Devon, stuck now for some weeks at No.18. Despite being the right sort of place, Dartington Hall failed us. As did Buckfast Abbey. I had to settle for more pictures of the handsome young araucaria araucana in the Abbey gardens. Earlier pictures to be found at reference 2.
As far as I can make out, last time there were eight rosettes, with a hint of a new rosette at the very top, while this time there were nine, again with a hint of a new rosette at the very top. Perhaps each year's spurt of growth starts with a new rosette? Next time I must remember to make measurements and counts so that I can properly track its growth.
In the meantime, I have still not managed to work out the system for the leaves, for their geometry. Are they spiral or what? But I did make one observation. The branches out from the main stem, the trunk if you will, are arranged in rosettes at regular intervals up the stem. I think usually four to a rosette, but sometimes as many as six. Not fixed like the number of petals of a buttercup. While the branches out from subordinate stems are all in slightly less regularly spaced opposite pairs. Somehow whatever is generating the lateral shoots knows whether to do four or more or just the two.
One device would be for the cells making up the stems to contain a flag, set to TRUE in the first instance, but set to FALSE in any stem that is generated from that cell. Then the cell generates a rosette when its flag is TRUE, an opposing pair otherwise. But will I ever get to know the sort of botanist who could confirm whether or not there is a mechanism of this sort?
Reference 1: https://en.wikipedia.org/wiki/Araucaria.
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