Dear Filip, obviously this can vary depending on the used metric system. Schröder (Kochia 12: 37-67) gives following remarks:

linea - 1/12 Zoll = 2.1 mm, or 1/10 Zoll = 2.54 mm.

pes/pedalis - e.g. English foot = 304.8 mm; Saxon foot - 283.2 mm; Prussian foot - 313.85 mm.

I am not aware of any unifying attempts of botanists of the 19th century for the metric systems, so you might have to look where you desriptions come from...

For poll./pollicaribus (obviously inch?) this might be the same.

Best wishes Michael

Thanks a lot, Michael. This is the description I am talking about: https://www.biodiversitylibrary.org/item/91244#page/51/mode/1up

Best wishes, Filip

Great, thanks a lot Sergei!

All the best,

Filip

Io prnso piedi, pollici e linee francesi, in vigore prima del sistema metrico introdotto da Napoleone (see Wikipedia)

Grazie a tutti per il vostro aiuto, ora è tutto chiaro.

I think it depends a bit on the country and time of the publication, how long a foot (pedalis) or thumb (pollicaris) is supposed to be, but surely the one is around 30 cm, the other one about an inch long.

Best regards, Fred

I looked at the original text via the link as posted by @Filip Verloove

I think given the fact that the text gives broad ranges (e.g. 1–2 ½ poll. length for the leaves), we do not need to be overly concerned about the marginal country-specific differences in length terminology

We may assume that the units are French (given the authors and place of publication). What's a tad off, though, is that the publication in question dates to 1836 to 1840, yet uses pre-revolutionary measurement units. Anyhow...:

pes = ~32.48 cm (pied du roi)

pollex 1⁄12 pied = ~27.07 mm (pouce)

linea 1⁄144 pied = ~2.256 mm (ligne)

@Filip Verloove, for all practical purposes, given the broad range of descriptions in the original text, you can just substitute the values in the publication with the relevant UK Imperial units:

pollex—inch

pes—foot

linea–line