Arthur Healy (1917-2011), was a weed scientist at Botany Division of the Department of Scientific and Industrial Research, which was the Government's science research arm from 1926 to 1992. Arthur's extensive herbarium collections of New Zealand weeds are the foundation for our knowledge of introduced plant biodiversity, but he wasn't just a collector, he experimented as well, and importantly he interpreted the significance of his findings for New Zealand. One of his simple experiments was to plant the fluff that accumulated in his trouser cuffs on overseas trips, to see what seeds had lodged there. Others were to see what grew out of packing straw and birds' nests. These experiments demonstrated the need for more effective biosecurity at our borders and showed how weeds spread and got established. They remind me very much of Charles Darwin's experiments.
|Arthur Healy (DSIR)|
Annual herbs are ones that complete their life cycle within a year. They get only one shot at flowering, so plants that die without managing to produce any seeds don't leave any offspring for the next generation. Over the centuries, the annuals that succeeded were those that were genetically predisposed to flower and make seeds, however small and under-resourced they might have been. Some of the weeds from footpath cracks and the shallow dusty soil of roadside gutters were much smaller than anything described in the Floras. I remember Arthur's specimens of opium poppies just 1-2 cm tall, with tiny flowers a few millimetres across. One had a seed pod that had room for just a single seed, all that starved plant could manage, but perhaps enough to pass its genes on for another generation.
|Cirsium vulgare, called Scotch thistle in New Zealand.|
|Hemlock, Conium maculatum.|
Thus the two tails of the normal distribution of plant height might often get neglected for a herbarium collection, and this could be reflected in the plant sizes that are published in scientific descriptions. By selecting the most aesthetically pleasing plants for the collections, are we biasing the information they hold? (However, I checked a few plant sizes in Flora Europaea and Flora of New Zealand, and I think they're pretty good overall. They do give the tall extremes at any rate, but maybe don't always include the smallest sizes.)