The Mullein (Verbascum Thapsus) is a very striking plant. It is high and clearly gray-woolly. Even without his yellow flowers, you can recognize him. The Mullein and related types were extensively used for all kinds of purposes: as medicine for stubborn cough, soothing oil for face pain, dyes, etc. The most curious use is to catch fish with it. Bruised blades were thrown into the water. That had to be still water. In the leaves, there is a substance that hinders the gill effect of fish, so that they come to the surface.
The genus name ‘Verbascum’ is a corruption of ‘barbascum’ which means ‘bearded’. That refers to the felty hair on the leaves of the plant. The ‘Thapsus’ species designation comes from the island of ‘Thapsos’ where a paint plant was found to dye fabrics yellow. The Mullein was also given that name because yellow dyestuff was also extracted from it.
Energy transfer measurements were carried out for normal and hairless leaves or Verbascum thapsus, in a wind tunnel. Leaves with the dense hair present were warmer than hairless leaves. This was shown to be due to a thicker boundary layer then that of normal leaves. Boundary layer resistance to heat and water vapor loss was higher for normal than for hairless leaves, resulting in lower convection and transpiration from the normal hair-covered leaves. Differences in transpiration resistance were correctly predicted by heat transfer theory. The hairs had little effect on radiation absorption by the leaves.
In the past, the soft, fine hairs on the leaves were used to make tinders for lighting the fire.
Prepared slide by Lieder www.lieder.com
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