Before measurement standardisation
Prior to the general adoption of the smaller units of the metric or imperial systems, botanists used traditional units related to human body parts or other natural objects. This relationship can also be seen in the historical development of units, the ‘foot’ being perhaps the more obvious. The ‘inch’ was originally the width of the human thumb, but was decreed by King Edward II of England in 1324 to be the length of “three grains of barley, dry and round, placed end to end, lengthwise”.
As thick as…
I have, for no other reason than my own amusement and with no claims to accuracy, endeavoured to establish measurements of other historical units used in phycological literature. These have mostly been taken from Dawson Turner’s ‘Fuci’ (1809, 1811) but also the writings of William Henry Harvey, everyone’s favourite nineteenth-century phycologist. Most of these measurements related to the thickness of quills from birds such as wrens, sparrows, blackbirds, geese and swans or other animals such as hogs…. with Harvey describing the frond of Asparagopsis armata as being ‘twice as thick as a hog’s bristle’.
Harm a hair on your head
Turner even used human hair as a unit of measurement when describing Fucus asparagoides. However, hair width can vary. My own scalp hair is 36–40 µm in diameter and my facial hair is considerably stouter at 100–110 µm diameter. Although over the last decade, my own hair is becoming thinner, but I will assume that is a density measure, not the actual fibres! This makes me wonder if any follicly challenged early taxonomists would ambush their colleagues to pluck hairs for units of measurement to complete their own taxonomic descriptions.
More interesting facts about unusual units of measurement can be found in ASBS Newsletter 201.
